Labour has piled pressure on Home Secretary Theresa May to explain what happened with regards to the decision to relax UK border controls this summer.
Opening a heated debate on the row on 9 November 2011, shadow home secretary Yvette Cooper said Parliament and the public needed answers on the "fiasco".
Ms Cooper said border agencies had told of "repeated cases where adults were not having passports swiped with no checks against the watch list".
She demanded to know "who authorised what" and asked Mrs May what advice she was given, the precise terms of the pilot she authorised and what she had communicated to the borders agency.
The home secretary mocked Ms Cooper's "sudden interest in immigration and border control" and attacked the record of previous Labour governments.
Defending the pilot scheme, Mrs May offered initial statistics showing an increase in the detection of illegal immigrants and the number of fraudulent documents seized, as evidence of its success.
She maintained she had not authorised a further relaxing of border controls, telling MPs: "In fact I stated explicitly in writing that officials were to go no further than what had been agreed in the pilot."
UK Border Force chief Brodie Clark was suspended last week by UK Border Agency chief Rob Whiteman, who says Mr Clark admitted authorising staff on a number of occasions to go beyond ministerial instructions. Mr Clark has since resigned, describing Mrs May's version of events as "wrong".
Chris Bryant, winding up the debate for Labour, claimed the scheme signed off by Mrs May was not a pilot but a "change of policy", adding that the home secretary "hasn't the decency to own up".
He also blamed Immigration Minister Damian Green who he described as being "a nicer man than his politics".
But Green accused Mr Bryant of "walking the line between opportunism and hypocrisy". He maintained the pilot was designed to strengthen the country's borders, telling MPs it had been a success.
The debate culminated in a vote in which MPs rejected Labour's motion calling for the publication of all communication between the Home Office and UKBA on the level of checks over the summer, by 300 votes to 247, a majority of 53.