Prime Minister Gordon Brown apologized Wednesday for the "inconvenience and worries" caused by the British government's accidental loss of computer discs containing detailed personal information of 25 million citizens.

British Treasury chief Alistair Darling looks through a rain-soaked car window as he arrives at the House of Commons in London on Wednesday.
(Peter Macdiarmid/Getty Images)

During a heated question period in the House of Commons, Brown tried to reassure the country that people's personal details gathered by Britain's tax and customs service were safe following one of the biggest security breaches in the country's history.

Two computer discs that went missing while being sent from one government department to another contained names, addresses, birth dates, national insurance numbers and — in some cases — banking details for nearly half the country's population.

"I profoundly regret and apologize for the inconvenience and worries that have been caused to millions of families that receive child benefits," Brown said. "We have a duty to do everything that we can to protect the public."

Treasury chief Alistair Darling said the discs contained details of the 7.25 million families in Britain claiming the child benefit — a tax-free monthly payment available to everyone with children.

He said the delivery was not being tracked and was missing for three weeks before any alarm was raised.

The discs were password protected but the information on them was not encrypted, officials said.

Conservative Leader David Cameron said the Labour government has "failed in its first duty to protect the public" and called for Darling to resign or be dismissed.

"What people want from their prime minister on a day like this is to show some broad shoulders, be the big man and accept some responsibility," Cameron said.

No evidence of criminal activity: Treasury chief

Brown said he had asked security experts to work with government departments to check their procedures. He said the information commissioner also would be given the power to carry out spot checks on government departments.

The prime minister also backed the embattled Darling, who prompted gasps from opposition members on Tuesday when he revealed the lapse.

Darling insisted there was no evidence the data had fallen into the hand of criminals and said police were involved in a hunt for the missing discs. He said banks had been told to look for signs of suspicious activity.

"The police tell me there is no evidence there has been any criminal or unusual activity," Darling said.

Darling, already rocked by fallout from the run on troubled mortgage lender Northern Rock, said he was not going to resign.

"I am not going to start running away from things when things get difficult," he told BBC radio. "It is difficult, it is unwelcome in every respect, and I am determined to see it through."

With files from the Associated Press