Border checks at Portsmouth’s ports were relaxed under a controversial pilot scheme authorised by Home Secretary Theresa May this summer, it has emerged.
In a letter to the Commons Home Affairs Select Committee, Mrs May confirmed the pilot scheme, which suspended the checks on biometric passports of EU travellers, was used in Portsmouth as well as Aberdeen, Belfast, Bournemouth, Bristol Airport, Cardiff, Coquelles, East Midlands, Edinburgh, Exeter, Glasgow, Harwich, Leeds Bradford, Liverpool, London City, Luton, Manchester Airport, Newcastle, Newhaven, Norwich, Plymouth, Poole, Prestwick and Stansted.
Fresh evidence released by Labour also showed that passengers on private jets were let into the UK without even being seen by border officials.
The latest disclosures will put further pressure on the under-fire Home Secretary as the former head of the UK Border Force, who quit his post over the border checks row, prepares to be questioned by MPs tomorrow.
Brodie Clark, 60, who resigned last week after a 40-year career in the Home Office, is expected to say he only acted to relax border checks because he was required to do so by the police to prevent overcrowding.
Leaked emails between UK Border Agency (UKBA) officials showed the controls were eased a total of 260 times in one week alone this summer.
Other leaked documents showed passengers on private jets were able to enter the UK without being seen by border officials, raising fears among staff that security was being compromised.
One UKBA official complained to managers about not even being “allowed to physically see the passengers”, saying it was “at odds with national policy” and “is creating an unnecessary gap in border security”, the emails showed.
Government estimates show there are between 80,000 and 90,000 private jet flights every year.
Further leaked emails showed Mrs May’s pilot scheme to relax border controls - referred to as level two checks - was used 260 times in the sixth week of the trial, the week ending September 16.
This compared with 100 times in its first week and 165 in week nine, ending October 9.
Mr Clark has denied extending the scheme improperly and accused Mrs May of blaming him for “political convenience” last week, saying her comments were “wrong”.
He resigned to pursue a case of constructive dismissal which could lead to a payout of up to £135,000 after Mrs May was accused of hanging him out to dry over the controversy.
She repeatedly told MPs that Mr Clark reduced the checks without ministerial approval.
The row intensified over the weekend when it emerged coach passengers have been allowed into the UK without being properly checked by border staff for four years.
Labour published emails from a UKBA official based at Durham Tees Valley Airport who said relaxed checks at the port brought in in March were “creating a situation where we are not able to secure the border as robustly as we would like to, for no justifiable reason”.
“We have no way of checking whether the handling agent information is correct or even if the number of people arriving on the plane matches the number we have been advised,” the official said.
But managers replied that there was “a new national GA (general aviation) strategy being rolled out” which was “consistent with national policy”.
Managers added that they were confident that the risk posed by the private jets could be met by “robust risk assessment and risk testing”.
One manager also tried to reassure the officials that “there will be no accusation of dereliction of duty as long as the procedures have been followed and the appropriate checks done by the officers”.
The figures showing the number of times border checks were relaxed were disclosed in leaked UKBA documents encouraging staff to use the new level two controls whenever it was possible to do so.
Managers told staff they were “trying to convince the Home Secretary and the Immigration Minister that we can operate successfully a risk-based system at the border without compromising border security”.
The scheme fell within the “use it or loose (sic) it” category, the documents said, and under-use would lead to ministers asking “why we made such a fuss about it”.
The emails were prompted by concerns that the Border Force North was using the relaxed system of checks on fewer occasions than staff based elsewhere in the country.
Shadow home secretary Yvette Cooper said: “This is startling new information about the scale of the borders fiasco.
“Ten days on there are even more questions than answers about what on earth was going on at our borders this summer.
“Last week the Home Secretary told us that no one had been waived through without checks this summer. But these documents show passengers on private flights weren’t even seen.
“Last week the Home Office wouldn’t admit to having figures about how often checks were downgraded.
“Now we know those figures exist, and that checks were downgraded 260 times in one week alone - potentially for hours each time.”
She called for Mrs May to release the full facts and figures immediately, saying as long as she refuses to do so, “people will think she has something to hide”.
A UKBA spokeswoman said: “It is not true that we don’t carry out passport and warnings index checks on private flight passengers and will deploy officers to airfields where we have concerns.”
Provisional figures also showed there were 10 million journeys through the UK’s ports in July 2011, and another 10.2 million in August 2011 - the summer peak periods at the centre of the border checks row.