The British foreign secretary admitted Friday that her government was aware of a secret CIA prison network before President Bush acknowledged its existence in September.

Foreign Secretary Margaret Beckett made the admission in a written response to a parliamentary question.

A a recent speech, Bush included a reference to the "existence of a detention program operated by the CIA." Bush said 14 high-value detainees — including the suspected mastermind of the Sept. 11 attacks, Khalid Sheik Mohammed — had been transferred from clandestine centers to the prison at Guantanamo Bay, Cuba.

"Prior to this speech, we were aware of the existence of a secret U.S. detention program only in general terms," Beckett said in response to a lawmaker's question.

A Foreign Office spokesman, speaking on customary condition of anonymity, said the statement was the first confirmation Britain had prior knowledge of the secret prisons.

An Intelligence and Security Committee report quoted an unnamed agent for the spy agency MI5, who said the U.S. was "holding some Al Qaeda members in detention, other than at Guantanamo, but we do not know the locations or terms of their detention and do not have access to them."

The agent told the committee, a panel of lawmakers which meets in secret to scrutinize spy agency work, Britain had received high-value intelligence from the detainees, "some of which has led to the frustration of terrorist attacks" in Britain.

A draft European Parliament report released Nov. 28 concluded that 11 European Union governments — including Britain, Poland and Germany — knew about secret CIA prisons operating in Europe.