A leading doctor has branded those attempting to jump the queue to get a Covid jab as "morally reprehensible".
Dr Vin Diwakar, NHS England regional medical director for London, said he was "horrified" to hear how "unscrupulous people" were looking to secure a vaccination against the deadly virus before their turn.
Home Secretary Priti Patel echoed the sentiment but declined to confirm whether the Government was considering introducing fines for those looking to skip the wait.
The comments come after reports emerged that links to the Swiftqueue system, which is used to book jabs for NHS staff, were being shared online.
Speaking at a Downing Street briefing on Thursday, Dr Diwakar said: "People are being called in priority order so that we can vaccinate those most at risk of serious illness first.
"That is why I was horrified to hear reports that some unscrupulous people have used links shared with them to try and falsely book a vaccination appointment.
"To seek to do this is denying some of the most vulnerable people in our community a life-saving vaccine.
"Let me be really clear about this: it is morally reprehensible to try and jump the queue and anyone who books to get the vaccine fraudulently will be turned away."
Downing Street told reporters that people should not try to jump the queue using the Swiftqueue system.
The Prime Minister's official spokesman said measures were in place to prevent people getting the vaccine as a result of making a "false online declaration".
"Nobody should be seeking to queue-jump, we have set out why we are prioritising those we are, given the increased risk that those groups face," the Number 10 spokesman said.
Ms Patel repeated Dr Vin Diwakar's rebuke of those trying to skip the vaccine queue as "morally reprehensible" and stressed that such behaviour would be denying a vaccine to those who are at highest risk of dying from Covid-19.
But asked about the possibility of introducing fines for those trying to exploit the system, the Cabinet minister said only that "all our measures are under review".
The vaccine roll-out is being targeted at the four top priority groups, as recommended by the Joint Committee on Vaccination and Immunisation (JCVI), which includes care home residents and staff, frontline NHS staff, the over-70s and the clinically extremely vulnerable.
Ministers are targeting offering everyone within those top four groups a jab by mid-February. Every adult in the UK will be offered inoculation by September, the Government has previously confirmed.
Ms Patel added: "Quite frankly right now our world-class, world-leading vaccine roll-out programme is there for the most vulnerable people – we've prioritised our cohorts and our groups – and our focus is on getting that vaccine to the most vulnerable to make sure we protect them and obviously protect others in the community as well."