The row over the decision to relax the UK's border controls has dominated exchanges at prime minister's questions.
Opposition leader Ed Miliband asked David Cameron how many people had been let into the country as a result of the decision.
Addressing the Commons on 9 November 2011 Mr Cameron said it was important to "be clear about what did and did not happen".
He said the head of the UK Border Agency, Rob Whiteman, had rightfully suspended UK Border Force chief Brodie Clark after learning that he had authorised staff to go further than ministerial activity on border relaxation. Both he and Home Secretary Theresa May supported the decision, he added.
Mr Clark stepped down on Tuesday after saying that Mrs May's claim that he had gone further than ministers had authorised was "wrong".
Mr Cameron gave his full backing to Mrs May telling the House that the pilot scheme she had launched had resulted in "more arrests, more fire arms seized, more fraudulent documents found".
But the Labour leader said it was "not good enough" that the prime minister could not say how many people had been let into the country under the "relaxed border controls".
He accused Mr Cameron of evading responsibility and claimed that the government's policy was a "fiasco".
Mr Cameron retorted that his government had done more on immigration and securing the country's borders in 18 months than Labour had in 13 years.