Proposals by the head of the UK border force for controls to be relaxed further prior to the start of a pilot scheme this summer were rejected before he went ahead with them, Home Secretary Theresa May said today.
Mrs May, who said she had no intention of resigning, told MPs that Brodie Clark wanted more discretionary controls than she was prepared to sign off - and then brought them in secretly anyway.
But the FDA, the trade union for top civil servants, accused the Home Secretary of treating Mr Clark with contempt, saying she was "declaring him guilty before he has had a chance of responding in any formal process".
Paul Whiteman, the FDA's national officer, added that Mr Clark, who has since been suspended, would agree to appear before MPs to answer questions over the scandal which saw relaxed border controls during the summer.
"It is astonishing that the Home Secretary has chosen to compound the prejudice to Mr Clark by declaring him guilty before he has had a chance of responding in any formal process," Mr Whiteman said.
"It cannot be right that the minister with responsibility for a department that should be grounded in justice should treat any official with such contempt.
"Mr Clark notes that he is either to be invited or summoned to appear before the Home Affairs Committee. He intends to fully co-operate with that request."
Earlier, Mrs May told MPs she had rejected Mr Clark's proposed changes in favour of a more limited pilot scheme, designed in part to reduce queues at airports.
But Mr Clark went further, scrapping key checks against a Home Office database without ministerial approval, she said.
"Those wider changes were ones which I rejected," she said.
Mrs May added that in setting out the terms for the pilot, "there were certain things that were suggested that I was not prepared to accept".
She said: "I take full responsibility for my decisions and actions related to the pilot, but Brodie Clark must take responsibility for his actions."
Mr Clark wanted his officers to be able to use their discretion so they could feel valued and get something out their jobs, rather than simply rubber-stamping forms like robots, aides to Mrs May said.
But he acted without ministerial approval.
The number of suspected terrorists, criminals and illegal immigrants who entered the country as a result of the move will never be known, Mrs May said.
But figures for August last year showed 10.5 million passengers coming into the UK, including 2.5 million people from outside the European Economic Area (EEA).
David Cameron later told MPs that what happened at the UK Border Agency (UKBA) was not acceptable.
"It is very clear to me that the Home Secretary did undertake a pilot scheme - a pilot scheme that was in some ways successful in terms of the number of arrests were up by 10%," he told the Commons Liaison Committee.
"But it is also clear that there was activity going on by the UKBA that is not acceptable, that was uncovered by the inspector. It has been stopped, the person responsible has been suspended.
"But clearly this is not acceptable. It is not acceptable that it went on for so long."
Labour has accused the Home Secretary of giving the "green light" to the unauthorised policy, pointing to UKBA guidance for border force staff.
The memo, dated July 28 2011, said: "If, for whatever reason, it is considered necessary to take further measures, beyond those listed above, local managers must escalate to the border force duty director to seek authority for their proposed action."
But Mrs May said the guidance "does not allow a decision to be made to significantly change the checks at the border" and was simply part of health and safety measures, should people start becoming ill or fainting in long queues at ports.
Mrs May said officials have been able to relax border checks for several years "in order to ensure flows through" and help prevent health and safety issues.
The paragraph in the memo, or operational instruction, enabling this "is something that has been appearing in documents for some time", Mrs May said.
She also told MPs on the Commons Home Affairs Select Committee that the intended pilot scheme "did not in any way put border security at risk".
Mrs May said she received three of four reports on the operation of the pilot scheme, with the fourth being sent back before it reached her because it did not provide enough information.
More regular weekly reports were kept at the ports and were not routinely passed to the Home Office, it is understood.
The inquiries into the scandal will seek to establish where and when the pilot scheme was used, and how the secret unauthorised scheme operated, with potentially hundreds of staff applying the relaxed regime.
Three senior staff, including Mr Clark, have been suspended and those responsible will be punished "to make sure that border force officials can never take such risks with border security again", Mrs May said.
She added: "The UKBA of today will not be the UKBA of tomorrow."
The Public and Commercial Services union (PCS) has claimed that border controls were relaxed to keep queues down despite cuts to personnel, but Mrs May has denied this.