Chester Zoo bosses have warned the park is at 'risk of extinction' and could end the year up to £24million in debt amid coronavirus lockdown.
Managers say the Cheshire site is 'Covid secure' and could open with limited numbers - but the Government has ordered the zoo to stay closed 'indefinitely'.
Jamie Christon, the zoo's chief operating officer, revealed the 126-acre animal park is now 'fighting for survival'.
Zoos across the country were forced to close to prevent the spread of coronavirus on March 23, but thousands of animals still need to be fed and looked after.
'This change in law has flicked a switch for us and, heartbreakingly, our lights are now flickering,' he said.
Managers say the Cheshire site is 'Covid secure' and could open with limited numbers - but the Government has ordered the site to stay closed 'indefinitely'. Pictured, dwarf mongoose triplets were born at Chester Zoo last month
'Not being able to open, despite being a huge outdoor site with all the necessary safety measures in place, is having a devastating impact on the future survival of this much-loved charity zoo.'
As visitor number continue at zero for the foreseeable future Mr Christon said the zoo's huge outgoings 'will financially cripple us'.
Launching the Save Our Zoo appeal on Wednesday, the zoo said the loss of 97 per cent of its income from visitors was having a 'devastating impact'.
'Not being able to open, with such massive outgoings, puts the future of the zoo itself at risk of extinction,' he added.
The visitor attraction needs £1.6 million a month to keep going, including £465,000 a month to care for the animals, a spokesman said.
As visitor number continue at zero for the foreseeable future Jamie Christon, the zoo's chief operating officer, said the zoo's huge outgoings 'will financially cripple us'. Pictured, five penguin chicks hatched at Chester Zoo in March and April
More than two million people visited in 2019 and 'virtual tours' have been shown online during lockdown.
Meanwhile, people have been allowed to gather in groups of up to six, including with others from a different household, in outside spaces such as parks and beaches.
This caused controversy over the weekend when thousands of beach-goers flooded to the seaside, including Durdle Door in Dorset, and piles of rubbish were abandoned in parks and beauty spots.
Mr Christon said: 'While we see pictures of public beaches, parks and UK beauty spots busy with people, our zoo - a huge outdoor space, with 16km of pathways, and numerous measures in place to ensure that we can provide a safe environment for guests - sits empty.'
The charity also has 80 global projects to prevent the extinction of species in the UK and across the world.
Directors and staff have taken voluntary pay cuts, half of the workforce has been placed on furlough and development projects have been put on hold as the zoo tries to offset the financial loss.
Meanwhile international conservation charity Zoological Society of London's (ZSL) Director General Dominic Jermey described the ban on zoos opening as 'simply bizarre'. Pictured, an alpaca gets a lockdown haircut at London ZSL
Mr Christon said: 'Chester Zoo contributes over £83.1 million to the regional economy, supports over 1,700 jobs, protects wildlife in more than 30 countries around the world and engages over 150,000 young people - the future of our planet - every year.
'At a time when global environmental pressures escalate, the seriousness of losing a conservation charity cannot be stressed enough.'
A spokesman for the Department for Environment, Food and Rural Affairs (Defra) warned it was 'vital' lockdown restrictions weren't eased too quickly.
They added: 'We understand the challenges faced by zoos and aquariums during these unprecedented times but it's vital that we do not move too quickly in reopening to ensure public health is protected.
'We have provided a £14 million support fund to ensure zoos are able to continue to care for their animals.
'Alongside this, work is ongoing to understand how and when zoos and aquariums may be able to reopen in a safe way to the public whilst maintaining social distancing.'
A £14 million fund to help zoos look after animals in the face of pandemic closures was announced by the Government. Pictured is London Zoo, Regent's Park, amid lockdown
Some 39,728 people have now died from coronavirus in the UK, with the country's number of infections rising above 280,000.
A spokesman for Chester Zoo said the Government's Zoos Support Fund was providing help to smaller organisations but that the larger charities were not eligible for support.
Meanwhile international conservation charity Zoological Society of London's (ZSL) Director General Dominic Jermey described the ban on zoos opening as 'simply bizarre'.
He revealed the charity's zoos, which include London and Whipsnade, have planned to introduce a range of safety measures including more places for visitors to wash hands, two-meter distance markets and one-way routes.
'We find it simply bizarre that we have been told not to reopen ZSL London and Whipsnade Zoo to the public, despite having explained to government in great detail how we have redesigned the whole experience at our zoos to make them COVID-secure,' he said.
Dartmoor Zoo in Devon was able to stay afloat after £44,000 of donations came in to support it through the coronavirus pandemic
'ZSL's zoos should be part of the solution to COVID, providing COVID-secure outdoor experiences where a population emerging from lockdown can visit with confidence; instead, the longer we stay closed, the less likely we are to survive the lockdown.'
Mr Jermey compared the virus to WW2, when zoos were allowed to stay open, and insisted they should be opened up to visitors to 'boost morale'.
He added: 'We believe that our zoos have a vitally uplifting role to play during these still-challenging times - safely connecting people to the natural world.
'Reopening will be an important step towards securing ZSL's future but is by no means an instant fix: as an international conservation charity which relies heavily on zoo ticket sales to fund our vital work, after months of enforced closure we will still urgently need support.'
The British and Irish Association of Zoos have complained about the absence of 'clarity from Government on the plans to reopen zoos'.
Giraffes Maggie and Molly stand under a sign showing support for the NHS at ZSL London Zoo, as the UK continues in lockdown to help curb the spread of the coronavirus
A spokesman said: 'The next Government review point of reopening closed businesses will be June 18th for a potential implementation of step three in phases from July 4th.'
They revealed their zoos were planning on implementing a range of safety measures including online ticketing and time slots, sanitation stations and a one-way system 'where appropriate'.
'IAZA believes that our members, with social distancing measures in place, can offer a controlled and significantly safer day out than many alternatives, similarly to ticketed gardens such as Kew Gardens and National Trust sites, which have been able to successfully reopen,' the spokesman added.
Dominic Jermey, who said zoos were in a 'very challenging' position
It comes a month after a £14 million fund to help zoos and aquariums look after their animals in the face of pandemic closures was announced by the Government.
Zoos and aquariums lost visitor income after being forced to shut due in the lockdown, but still face the costs of looking after the animals in their care.
The Government said the funding would help zoos cover costs relating to keeping the animals and ensuring welfare standards are upheld - helping pay for things such as feed, heating and security.
The Environment Department (Defra) also said it would continue to work with some of the largest zoos to discuss additional concerns about funding in the longer term.
Lord Goldsmith, Animal Welfare Minister, said: 'Even in these very difficult times, the Government remains absolutely committed to high standards of animal welfare.
'We know that many of our zoos are facing real pressure as a consequence of coronavirus, and we have made support available to them, including business rates relief and the business interruption loan scheme.
'This new Zoo Support Fund is designed to help those that need additional support to maintain the welfare of their animals.'
Individual grants of up to £100,000 are available for English establishments covered by the Zoo Licensing Act, and the Government hoped the £14 million funding would support the sector, particularly smaller zoos.
ZSL zoos have been closed to visitors since March 20-21 due to the pandemic lockdown, but staff have remained on site to look after the animals
Chief Secretary to the Treasury, Steve Barclay MP, said: 'Zoos don't just provide a great family day out, but are vital for education, protecting endangered species and conservation work.
'This fund, on top of the existing package of support we're offering businesses, will mean that zoos across the country are helped to get through the coronavirus outbreak.'
Dr Madelon Willemsen, chief of the British and Irish Association of Zoos and Aquariums (BIAZA), said zoos and aquariums had gone to 'extraordinary lengths' to cope with the pandemic while looking after animals despite the lack of income.
'We are pleased to have worked with Defra in shaping this much needed crisis support for zoos and aquariums.
'We continue to work to ensure those most in need have access to this and other forms of support.'