LONDON — Britain shook up its troubled border agency Monday after admitting that security checks at ports and airports had been suspended or applied inconsistently for the past five years.

Home Secretary Theresa May said an investigation had found that the U.K. Border Force, which staffs border posts at airports and ports, had "suspended important checks without permission."

She said lapses included failing to check half a million Europeans arriving on Eurostar trains against a government watch list.

May said the border force had also suspended fingerprint checks on visa holders without government approval, spent millions on new technologies it did not use and sent reports to the government "that were inaccurate, unbalanced and excluded key information."

May said the risk to Britain had been small since "no one was waved through, everyone had their passports checked" -- but the lapses were nonetheless unacceptable.

She told lawmakers in the House of Commons that the border force would be split off from its parent, the U.K. Border Agency, beginning March 1 to give it "a whole new management culture." She said the force would have "its own ethos of law enforcement" and be led by a former Wiltshire county police chief, Brian Moore.

The border agency will continue to handle other immigration-related tasks including issuing visas and handling asylum applications.

The head of the border force, Brodie Clark, was suspended in November after the government acknowledged that passport checks had been relaxed at 28 British ports and airports, including London's Heathrow Airport, during the busy summer travel season.

Clark insists he acted with ministerial approval and is suing for wrongful dismissal.

May said the Border Agency had been structurally flawed since it was set up by the previous Labour government in 2008.

"From foreign national prisoners to the asylum backlog to the removal of illegal immigrants, it has reacted to a series of problems instead of positively managing its responsibilities," she said.

The opposition Labour Party, however, blamed budget cuts by the Conservative-led government for the problems.

"The clear suggestion in this report is that the lack of staff may have increased the problem at the Borders Agency," said Labour home affairs spokeswoman Yvette Cooper.

"This mess got worse and escalated on your watch every month that went by," she told May.

Like other government departments, the Border Agency has seen job cuts as Britain seeks to trim spending by 80 billion pounds ($127 billion) by 2015.