Updated

Britain's interior minister said Monday it may never be known how many people entered the country without being matched against terrorism watch lists after border officials loosened checks to cut lines at immigration halls.

Home Secretary Theresa May acknowledged that she had sanctioned a trial under which border staff were encouraged to reduce checks on some visitors arriving into Britain, but claimed officials had strayed far beyond the agreement.

Three government officials have been suspended amid an investigation into allegations about widespread failures to inspect biometric passports, or to match adults against lists of possible terrorism suspects or immigration registers.

"As a result of these unauthorized actions, we will never know how many people entered the country who should have been prevented from doing so after being flagged by the warnings index," May told lawmakers in a statement to the House of Commons.

May said that an inquiry would report by January on what had gone wrong with the pilot program, implemented in late July at the height of the tourist season. She said the inquiry would make recommendations for changes.

Under the pilot program, border staff were permitted in some circumstances to use their judgment when deciding whether to check biometric passport information of adults from the European Union, or to cross reference children of EU nationals against watch lists.

An internal border agency memo shows that staff were able to temporarily downgrade security procedures to ease lengthy immigration lines, or to redeploy staff to focus on other passengers considered to pose a greater risk.

May told lawmakers that border guards had instead routinely abandoned checks on European passengers. In some instances, adults arriving via ferry or train from Calais also were not checked against Britain's warning index -- a database which includes details of individuals of concern and information related to lost or stolen passports.

She acknowledged that fingerprint checks of some non-EU members had also been halted.

"I did not give my consent or authorization for any of these decisions," she said. "Indeed I told officials explicitly that the pilot was to go no further than we had agreed."

In June, banned preacher Sheikh Raed Salah evaded border guards and entered Britain despite an order from May barring him because of his political activities.

Legislator Yvette Cooper, who leads on interior affairs for the main opposition Labour Party, said Britons would be "understandably appalled and shocked" to learn some border checks had been abandoned.

"She has blamed officials for relaxing the checks further than she intended, but she gave the green light for weaker controls," Cooper told May in the Commons.

May said border checks had previously been suspended in similar circumstances in both 2004 and 2008, under Britain's previous Labour-led government.

"Our task now is to make sure that those responsible are punished, and to make sure that border force officials can never take such risks with border security again," May said.