Passengers arriving at Leeds-Bradford Airport from overseas have been allowed to enter unchecked through Passport Control for a second time.

The revelation comes on the day that Government officials told a local MP that security at the airport had been tightened up after a similar incident in October.

Today MP Greg Mulholland, whose constituency includes the airport, said it "beggars belief" that it had been allowed to happen again.

Passengers arriving on an international flight on Monday were taken through the domestic arrivals gate due to a "human error" - avoiding normal checks to gain access to British soil.

Airport officials said that the mistake was quickly rectified, but one passenger on the flight said: "We were just allowed out as though we were arriving from another UK destination."

Critics have been quick to compare the incident to a security fiasco on October 24, which saw passengers arriving from Brussels allowed through Passport Control unchecked after they were mixed in with passengers arriving from Dublin.

Ironically, details of the latest incident came to light on the day that Otley MP Mr Mulholland received a letter from the Border & Immigration Agency responding to his concerns over that incident, which prompted Immigration Minister Liam Byrne to order an immediate investigation.

Mr Mulholland said: "It is even more unbelievable when the Chief Executive of the Border and Immigration Agency has written to me personally just this morning to assure me that the previous incident was a one-off and that measures had been put in place to prevent it ever recurring.

"This new blunder completely makes a mockery of these assurances, and raises fundamental questions about security procedures at Leeds Bradford Airport and the ability of those on the ground to make sure these procedures are being followed.

"I am again writing to the Home Secretary, this time to demand that people are held accountable and that this sort of thing must never happen again."

The letter, written by Lin Homer, chief executive of the agency, said the investigation concluded that, although processes in place at the time met the requirements of the port, the presence of a Dublin flight at the International Arrivals control had "created a unique situation".

He was aware that some passengers on the Brussels flight were "not seen immediately" by immigration officers, but added that there had been "no actual breach of the United Kingdom's border security".

The letter said: "In the light of the findings of the investigation..local procedures have been reviewed and strengthened to prevent a recurrence of such a situation. All parties have agreed that the International Arrivals control must not be used for non-international traffic."

Speaking of Monday's incident, a spokesman at Leeds Bradford Airport (LBA) said: "LBA can confirm that passengers arriving from Brussels on Monday, December 10 were taken into domestic arrivals due to a human error. This was quickly identified and corrected."

A spokesman for the Border & Immigration Agency said: "Every single passenger on this flight was checked by immigration officers. The Border and Immigration Agency meets every international flight arriving at Leeds-Bradford."

But one passenger, who did not wish to be named, said: "I was flying in from Brussels on the afternoon flight. The girl clearly thought she was greeting a domestic flight and brought people out through domestic arrivals, so there was no immigration or special branch. We were just allowed out as though we were arriving from another UK destination.

"I think it was very lax of the airport."

The error was described as "disturbing" by Councillor Neil Hunt, a Horsforth Town Councillor and founder member of the Leeds Bradford Airport Community Forum, set up to respond to the Government's airport expansion proposals.

Coun Hunt (Con, Victoria) said: "It's quite disturbing because there's potential, in the current world climate, for something nasty to happen. It is surely a systematic failure rather than human error. It is the inevitable consequence of the rapid expansion of low-cost international flights without the parallel expansion in the methods of operating as an international airport."

Shipley MP Philip Davies said: "There's huge public concern about illegal immigration and security.

"Everyone makes mistakes, but it's unacceptable for some mistakes to be repeated."