The former head of the UK Border Force today accused the Home Secretary of destroying his reputation and insisted that he was "no rogue officer".
Brodie Clark, who quit his 40-year career in the Home Office last week amid the border checks row, criticised Theresa May's actions as he told MPs that he did not extend or alter her pilot scheme of risk-based checks at the border in any way.
But he admitted using guidance designed for health and safety emergencies to suspend fingerprint checks at the UK's ports, actions which had no ministerial authorisation.
Mr Clark resigned at the height of the row, accusing Mrs May of blaming him for "political convenience", saying her comments were "wrong" and launching a constructive dismissal case in which he could net £135,000.
He told MPs: "Over 40 years I have built up a reputation and over two days that reputation has been destroyed and I believe that has been largely because of the contribution made by the Home Secretary."
"I am no rogue officer. Nothing could be further from the truth."
He admitted that fingerprint matching for non-visa holders was suspended on 50 separate occasions between May and July this year alone for health and safety reasons.
Under the guidance, key checks against a Home Office warnings list of terror suspects and illegal immigrants could be suspended, but only when emergency services or the port authorities thought it was necessary for public safety.
This could be when there were lengthy queues at the border, passengers being held on planes or planes not being able to land, the MPs heard.
He said he "would expect ministers to know that".
But he told MPs that he thought the warnings index checks were too important to remove, so told staff they could suspend fingerprint checks in those circumstances instead.
He admitted he did not ask ministers first, but insisted it was never done "as a matter of course".
"I did it to preserve the safety of the UK, not to weaken it," he said.
In terms of the pilot scheme, Mr Clark told the Commons Home Affairs Select Committee that Immigration Minister Damian Green had agreed that it could include the suspension of fingerprint checks.
But Mrs May overruled him and rejected that proposal before the scheme began.
Mr Clark, 60, said the issues surrounding the border checks row had been "confused by a conflation of two things" - the long-standing policy on dealing with critical health and safety issues at ports, and the Home Secretary's pilot scheme of more risk-based checks.
The health and safety measures had been "standard practice" since June 2007, he said.
He did suspend fingerprint checks under this policy without any approval from ministers, but insisted he had "never sanctioned that the high quality checking arrangement at our border should be adjusted to speed the flow".
But on the pilot, he was unequivocal, saying he "did not enlarge, extend or redefine the scope in any way".
Mr Clark said more risk-based checks like those in the pilot were needed and it was "wrong" for the Government to return to blanket checks.
He added that "eight million occasions of checking children against a security watch list produced only one spurious 'hit"'.
The pilot was about "better use of staff for improved performance", while the contingency arrangements were long-standing "pre-existing policy from 2007 which are there to protect the safety of people in particular circumstances".
Mr Clark left the committee room in Portcullis House, Westminster, through the "members only" door, avoiding his former boss, UK Border Agency (UKBA) chief executive Rob Whiteman, coming in through the public entrance.
Moments later, Mr Whiteman said Mr Clark admitted going beyond ministerial authorisation and that he was right to suspend the civil servant.
He said Mr Clark emailed him early on the morning of the suspension, saying: "Ministers said 'no' to this proposal (to suspend fingerprint checks in the pilot scheme), I consider that I complied with that, whilst at the same time there are provisions under which I have authorised it and ministers have never been aware of those provisions."
The UKBA chief told MPs: "Well, that's the same effect, isn't it?
"What I had was evidence from one of my senior directors that ministers were not aware what was going on under that separate provision, even though they had explicitly said what should take place under the provision they were aware of."
Earlier, asked whether ministers knew about the differences between the pilot and the operational guidance, Mr Clark said: "I would be surprised if they did not know these policies or understand them."
He went on: "I made no connection between business as usual under these circumstances and the pilot operation."
He also told the MPs his suspension had been "something of a nightmare" and "something which has taken over my life".
Mr Clark said he was suspended and offered retirement in the same meeting with Mr Whiteman.
He claimed Mr Whiteman told him there would be a "good package", including nine months' pay, and that he would give him "a good reference".
But Mr Whiteman denied offering the option of retirement, saying retirement was simply an issue the pair had discussed at the end of the meeting.
The possibility of retirement, which Mr Clark said he verbally agreed to accept, was later ruled out by Home Office permanent secretary Dame Helen Ghosh.
Mr Clark said: "The truth is, with 40 years of service in difficult posts across government, I had become very pragmatic and it was clear to me that there was no place for me in Rob Whiteman's forward-going UK Border Agency."
Former home secretary Alan Johnson told Sky News: "For me, this is all about the treatment of Brodie Clark.
"She (Theresa May) should not have, under any circumstances, fingered a senior civil servant when there hadn't even been a proper investigation into what happened.
"That is the terrible thing that she did, because she placed this civil servant in the invidious position of having to resign to defend himself.
"When you are the Secretary of State, you don't put senior officials who risk their jobs day in and day out for you, particularly in the Home Office, you don't put them in that position."
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