Science Minister George Freeman suffered a car crash TV interview this morning as he was unable to say when people under the age of 40 will be able to book their Covid booster jab.
Boris Johnson has pledged that all UK adults will be offered a third coronavirus vaccination by the end of January.
But ministers have still not published a detailed rollout plan setting out when people in their 20s and 30s will be able to book.
Mr Freeman was asked repeatedly this morning why the Government is yet to publish the plan and when younger adults will be able to book.
The minister could not give a firm answer and suggested people should 'contact their GP now' - despite health bosses telling the under 40s to wait to be called forward by the NHS.
Sky News presenter Kay Burley told Mr Freeman that 'the answer is you don't know the answer' as she said the minister's response was 'just not true'.
It came as the Government announced it has signed deals to secure 114million new Moderna and Pfizer jabs which will be delivered in 2022 and 2023.
The purchases appear to put a fourth coronavirus jab for British adults a step closer.
Mr Freeman hinted that a fourth round of jabs will be offered next year as he said 'we've got to make sure that our citizens are safe'.
Science Minister George Freeman suffered a car crash TV interview this morning as he was unable to say when people under the age of 40 will be able to book their Covid booster jab
Boris Johnson has pledged that all UK adults will be offered a third coronavirus vaccination by the end of January
Mr Johnson used a Downing Street press conference on Tuesday to announce that all UK adults will be offered a booster jab by the end of January as the Government takes action to slow the spread of the Omicron variant.
All over-40s can already book a booster but the rollout is not yet open to the under-40s as officials work out a timetable for the coming weeks.
Ms Burley told Mr Freeman that the nation had been promised a rollout plan as she asked where it is.
Mr Freeman replied: 'Today we have got all of the global pharma leaders here in London to announce another half a billion pound package into UK life science and as your report highlights, this pandemic isn't over and the UK is leading in both the science of defeating this virus and in the rollout package for vaccines here in the UK.
'We have procured another 114million doses so we have got the doses here for patients over the next few months.'
Ms Burley said: 'And in answer to my question?'
Mr Freeman said: 'We are working right now across government on how we both accelerate the rollout internationally of vaccines. The truth is we are not safe until the world is safe and the UK has led that charge.
'We have invested more per capita than any other nation, we are huge supports of Covax and at the G7 summit this summer we led the charge on how globally we support international rollout.
'Here in the UK our vaccine rollout programme is setting the benchmark and that is why we are able this year to not impose the very tough, quite draconian regulations, we had to last year, in a way that other countries are.'
Ms Burley said a rollout plan had been promised earlier this week and 'people don't know when they can have their boosters' as she asked again: 'Where is the plan?'
Mr Freeman said: 'The NHS have a plan, it is being rolled out and people can apply now.
'I have just had my text last night, my booster appointment has been offered for next week and people across my constituency and around the country are able now to get their boosters.'
He added: 'I would encourage everybody contact your GP, get on the app, book your booster jab. The NHS is there, we are rolling it out, we have procured the vaccines and we are leading the world in that rollout.'
Ms Burley again pressed for clarity on when people in their 20s and 30s will be able to book and Mr Freeman replied: 'So, if you contact your GP there are slight differences round the country but at the moment we are the first country to get to this point, we have got 80 per cent of the whole country double jabbed.
'We have got nearly 90 per cent of the whole country first jabbed and we are now rolling it out fast.
'Some GP practices are rolling slightly quicker than others and that is what you would expect but if people contact their GP now and go on the app they can book to get their booster jab.'
Ms Burley replied: 'Minister, that's not true. You can't get your booster at the moment if you are in you 20s. The question is we were told earlier in the week that there is a plan.
'I am just asking you where the plan is and when people in their 20s and 30s can book their booster?'
Mr Freeman said: 'Well the NHS are leading on that rollout. I haven't got at my fingertips today exactly which GP practices are making it available today.
'But we are accelerating that rollout and it is key and we are putting that in place so that the next generation, the next age cohort can get their booster jab as quickly as possible.'
Ms Burley hit back and said: 'The answer is you don't know the answer. Minister, if you are in your 20s you don't know when you can have the jab. Just admit to that because that is fundamentally the case, isn't it.'
Mr Freeman then said 'the case is that the NHS is rolling out the vaccine rollout' prompting Ms Burley to interrupt: 'You don't know.'
Mr Freeman continued: 'If you contact your GP and book it you will get your jab.'
Ms Burley said: 'That is not true, it is just not true. It is just not true minister.'
The bruising clashes came after the Government announced it has bought 114million extra doses of Pfizer and Moderna vaccines to be delivered over the next two years.
The bulk order has prompted speculation that people will eventually be offered a fourth jab and potentially even a fifth.
The order has caused a backlash as critics asked why the UK is buying more doses when the vaccine rollout in much of the developing world is so far behind countries like Britain.
Mr Freeman said: 'I think the British public would expect us to make sure that we're providing the supply to those in the UK, which is why we've just procured another 114 million doses, precisely to be sure we can deliver that rollout here in the UK as well.
'This is a balance. We've got to make sure that our citizens are safe and that the global vaccine rollout through Covax is supported, and that's what we're committed to doing and that's why today we've got, as part of that G7 follow-up, all the global leaders in vaccine science here in the UK at No 10 to make sure we are continuing to focus on it. It is an international challenge.'