Ministers say Boris Johnson's decision to delay Freedom Day is one of the reasons for the Tories' shock loss in last week's Chesham and Amersham by-election.
They told The Mail on Sunday that the Prime Minister's decision to postpone the lifting of social distancing measures from June 21 to July 19 'must have had an effect' on Thursday's vote, which saw the Liberal Democrats overturn a Tory majority of 16,000.
The private warnings came from Ministers who would be punished by party whips if they dared to speak out in public.
Ministers say Boris Johnson's decision to delay Freedom Day is one of the reasons for the Tories' shock loss in last week's Chesham and Amersham by-election
But senior backbencher and former Tory leader Sir Iain Duncan Smith said openly that postponing Freedom Day probably contributed to the Tory rout. He said: 'I suspect a number of Tory voters didn't vote, taking the view that as the Government decided not to get things moving again, they would stay at home on polling day.'
Last week's result stunned the Tory high command, leading to recriminations among strategists over the party's failure to detect – and arrest – the surge in support for Sir Ed Davey's party.
Tory backbenchers immediately warned Mr Johnson not to neglect the concerns of the party's southern heartlands in his eagerness to shore up support in ex-Labour seats in the North which turned Tory for the first time at the 2019 General Election.
Party HQ's post-mortem on the by-election shock in the Home Counties seat, which had never before failed to elect a Tory MP, focused last week on what Mr Johnson called 'particular circumstances' in the seat – opposition to the HS2 rail link which gouges through the local countryside, anger over plans for more housebuilding and opposition to Brexit.
The by-election saw the Liberal Democrats overturn a Tory majority of 16,000 in a shock result
Tory MPs added to the complaints list last night by saying the party's campaign itself was 'shambolic', with visiting Tory MPs allegedly told to simply deliver leaflets rather than knock on doors and talk to voters. 'The whole thing was terribly complacent,' one said. And last night, one senior Minister said that continuing the Covid restrictions had also played a part.
He said: 'Lots of Tory voters didn't like the extension of the restrictions and they just won't have bothered to turn out to vote.
'It was obviously Conservatives staying at home because the by-election was just a few days after it was announced they were being locked up for longer.'
The Minister insisted that without the Freedom Day delay, the Tories would have held the seat.
Another senior backbench figure said: 'A lot of people in the constituency will work at Heathrow or in the travel industry – which has been decimated by the quarantine restrictions – or have holiday homes on the Continent.
Liberal Democrat candidate Sarah Green makes a speech after winning the Chesham and Amersham by-election
'A lot are also self-employed or work in hospitality. It must have had an effect.'
Sir Iain backed up the analysis last night, saying: 'Boris Johnson's decision to postpone Freedom Day last week was undoubtedly one of the factors in Amersham and Chesham. There will many people in that constituency whose livelihoods depend on reopening the economy and getting back to work.
'They are people who run their own businesses and don't necessarily have the luxury of being on fur-lough or having comfortable, public-sector jobs that allow them to work from home.'
However, another senior party figure pointed to the concerns raised by former Prime Minister Theresa May over the proposed planning law changes which – despite Government denials – have raised fears of developers being able to concrete over huge areas of the South for new housing.
Mrs May has objected to the 'ill-conceived' planning reforms, designed to increase house-building and give younger people the hope of owning their own home.
She has also used a Commons debate to lambast the 'incomprehensible' Covid-related holiday ban which, she said, had left the country 'shut for business' despite the UK's world-beating jab rollout.
The senior party figure said: 'Theresa is speaking for the forgotten Tory supporters in the South who have voted for the party all their lives – not in just one Election.'
It comes as radio presenter Julia Hartley-Brewer accuses Downing Street of double standards for delaying Freedom Day for ordinary voters while ignoring the rules in No 10 and last weekend's G7 summit in Cornwall.
Writing in today's Mail on Sunday, above, she says the images of world leaders enjoying a barbecue on the beach 'proved to millions of Britons that the long-perpetrated mantra of 'we're all in this together' under lockdown restrictions is a lie.
'One by one, world leaders were seen to arrive at G7 wearing face masks and greeting each other with theatrical elbow-bumps. Yet then they were soon pictured happily drinking and eating together at a barbecue, arms around each other, unmasked faces just inches apart. The rest of us, whether we agree with the lockdown or not, were left infuriated and flabbergasted by this blatant disregarding of the rules. Any pub landlord who'd allowed such a large group to behave like this in their pub garden would have risked losing their licence.'
Tory MPs are also grumbling that Cabinet Office Minister Michael Gove was allowed to carry on work-ing in Whitehall earlier this month, despite being notified through the NHS app that he came into contact with someone with coronavirus following a trip to Portugal.
Mr Gove avoided self-isolation by taking part in a pilot scheme in which he had to take daily corona-virus tests in No 10 for ten days, although he had to self-isolate when he was not at work.
Tory MP Marcus Fysh, who voted against the lockdown delay, said the same system should be used for the wider public because 'it's useful to have one single set of rules in one system'.
Mr Johnson appeared to play down the by-election defeat, saying there were 'particular circumstances' in Chesham and Amersham. He insisted the Government was 'getting on with delivering our agenda for the whole country – that's what one-nation Conservatism is all about'.
The by-election was triggered by the death of former Cabinet Minister Cheryl Gillan.