London ? 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.

In 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 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.