The pressure on John Reid over the criminal records fiasco intensified amid claims that two of his junior ministers had been alerted to the crisis.
The Home Secretary has repeatedly denied that any ministers knew of the 27,500 case files - including details of 540 serious offenders such as murderers, rapists and paedophiles - that stacked up in the Home Office without being entered on the police national computer.
Last night, the Tories said that the position of two ministers was untenable after it emerged that the Association of Chief Police Officers (Acpo) had written to the Home Office in the autumn telling it about the files listing crimes committed by Britons abroad.
According to ITN, the letter concluded: "I recognise you may feel this is something the Home Secretary might want to be briefed about, given the obvious links to foreign national prisoners."
The letter was sent to Tony McNulty, the Police minister, in October and acknowledged by Joan Ryan, the junior minister for immigration, last month. It is understood to have outlined the problems faced in processing information about foreign convictions, but did not mention the backlog. A senior Home Office source dismissed ITN's interpretation of the letter last night as "bullshit".
Ms Ryan said on Tuesday: "It's the case that we knew nothing of this. As far as we are aware, no ministers knew of this until lunchtime today." And Mr Reid, making an emergency statement to MPs yesterday, assured the Commons he knew nothing about the backlog.
David Davis, the shadow Home Secretary, seized on ITN's claims, saying: "If this is true, the position of two ministers is untenable. We need to see the full copy of this letter. Acpo should now publish, including all replies. "
The Home Secretary faced further embarrassment after it emerged the Home Office also turned down a plea from police for help in tackling the criminal records backlog in October. He admitted there had been "fundamental flaws" in the system for processing information about Britons who had committed crimes abroad.
Mr Reid told the Commons he had ordered an urgent inquiry and said he had told police chiefs to accelerate the processing of the files. But Acpo said it had asked for extra cash to deal with the backlog in October.
Nick Clegg, the Liberal Democrats' home affairs spokesman, said: "John Reid is fast resembling Manuel from Fawlty Towers, who made a habit of declaring, 'I know nothing'. This mixture of ignorance and incompetence would be comic if it did not jeopardise public safety in the way that it has. "
Mr Reid told MPs that 280 of the 540 serious criminals were unaccounted for as ministers had received scant details from the countries where the crimes took place. He said the Criminal Records Bureau would now check if any offenders had mistakenly been given the all-clear to work with children or vulnerable adults.
He told the Commons: "The process for handling these notifications when they arrived in the UK was fragmented and piecemeal. There were, therefore, fundamental flaws in the sending of information and receipt of information." Mr Reid said the backlog of less serious offenders - about 27,000 - should be processed within three months.
The blame game
* In May, the Home Secretary, John Reid, described his department as " dysfunctional in the sense it doesn't work" and its immigration service as "not fit for purpose".
* Beverley Hughes, the Immigration minister, blamed an "excess of zeal" by managers anxious to clear a backlog for waiving checks on residency applications from citizens of eastern European countries about to join the EU.
* Nick Brown, the Agriculture minister, asked in March 2002 why he had abandoned plans to vaccinate cattle, with the result that thousands died from foot and mouth, said it was the fault of slaughtermen.