Attempts to jump the queue for early vaccination were criticised as "morally reprehensible" at a Downing Street Covid-19 briefing.
Dr Vin Diwakar, National Health Service England’s regional medical director for London, spoke of “unscrupulous people” trying to get round the priority list, putting the most vulnerable at risk.
And Priti Patel, the UK Home Secretary, said anyone booking a test fraudulently would be prevented from receiving the injection.
The UK gave priority for the first vaccines to those over 80, the most vulnerable and health workers, before next week moving on to those over 70.
There is pressure for police, teachers and other key workers to be moved up the priority list.
NHS staff take appointments on a Swiftqueue website but a link to the site was shared on social media, opening the possibility of people skirting the rules.
“Let me be really clear – it is morally reprehensible to try to jump the queue and anyone who books to get the vaccine fraudulently will be turned away,” Dr Diwakar said.
“If you are called for the vaccine, come forward, it could save your life. People are being called in priority order so we can vaccinate those most at risk of serious illness first.
“And that is why I was horrified to learn that some unscrupulous people have used links to try to falsely book a vaccination appointment.
“To seek to do this is trying to deny some of the most vulnerable people in our community a life-saving vaccine.”
Ms Patel said queue jumping was “morally reprehensible”.
"These individuals are putting the lives of vulnerable people at risk, the most vulnerable that have been prioritised by the government to receive the vaccine because they are vulnerable in the sense of not just contracting the virus, but could die from this deadly, deadly virus," she said.
Almost five million people have received the first dose of the vaccine, and a record 363,508 were administered in the past 24 hours.
Britain has been hit hard by the latest wave of the pandemic, with daily deaths routinely over 1,000.
The latest government data showed another 1,290 deaths and 37,892 cases. It brings the total number of fatalities to 94,580 since the pandemic began.
“We’re seeing the contagiousness of the new variant that we saw arrive just before Christmas. There’s no doubt it does spread very fast indeed,” Prime Minister Boris Johnson said.
“It’s not more deadly but it is much more contagious and the numbers are very great.”
Mr Johnson said it was “absolutely crucial” to follow lockdown rules “in what is unquestionably going to be a tough few weeks ahead”.
He said research, including the React study from Imperial College London, showed that current levels of coronavirus were still too high.
“I think it’s too early to say when we’ll be able to lift some of the restrictions," Mr Johnson said.
Just announced:
— Priti Patel (@pritipatel) January 21, 2021
We're introducing a new £800 fine for those attending 𝐡𝐨𝐮𝐬𝐞 𝐩𝐚𝐫𝐭𝐢𝐞𝐬.
This will double for each repeat offence up to a maximum of £6,400.
At this crucial time, please stay home.
Protect the NHS. Save lives. pic.twitter.com/Y4zNBhmZAz
Ms Patel also said that bigger fines for people at house parties would be introduced next week.
“The science is clear," she said. "Such irresponsible behaviour poses a significant threat to public health, not only to those in attendance but to our wonderful police officers who attend these events to shut them down."
The £800 ($1,098) minimum fine is an increase on the previous £200 penalty for a first breach of Covid-19 rules in England, and can be up to £6,400 for repeat offenders.
Martin Hewitt, chairman of the National Police Chiefs’ Council, said 250 fixed penalty notices had been issued to organisers of large gatherings since August.
Among his examples was a party in Brick Lane, East London, which was attended by more than 40 people who were “hostile to the police”, injuring three officers.
A party in Hertfordshire with more than 150 people was stopped by the police, while 50 people were at a dance party in Leighton Buzzard, despite police warning the organisers against it.
They were issued a £10,000 fine.
