A controversial job application website for junior doctors has been suspended, amid fresh concerns of security lapses.
Ministers have already agreed to review the online system
The Department of Health said it was investigating claims that doctors were able to read each other's messages.
The new concerns come a day after revelations that applicants' personal information could be freely accessed.
The MTAS website has been the subject of protests from junior doctors. The Conservatives say the system is in "complete crisis".
Channel 4 News reported that applicants had been able to see each other's files by changing two digits in the personalised web address given to each individual.
'Lack of confidence'
A spokeswoman for the Department of Health said: "We have temporarily taken the MTAS website off-line and are investigating allegations that registered junior doctors could deliberately access each others messages."
Shadow health minister Stephen O'Brien said there was a "serious lack of confidence" in MTAS.
"We need the government to act upon this immediately, even if they do find their lack of leadership embarrassing," he said.
"Until confidence is its security restored, I don't see how junior doctors can be expected to use MTAS."
Liberal Democrat health spokesman Norman Lamb said earlier he had written to the Information Commissioner asking him to investigate urgently the "extremely concerning situation".
In the letter he says: "The lack of consideration for the security of personal data in this case seems to constitute a serious breach of the Data Protection Act."
The web-based application system was introduced by the government to help place junior doctors in their chosen specialist fields.
But applicants have complained the system is unreliable, badly designed and fails to match the right people with the right jobs.