Ministers faced fresh questions over the alleged bugging of an MP after Government officials revealed they were alerted to concerns months ago.

Jack Straw was accused of losing control of his department after the disclosure that Tooting MP Sadiq Khan's visits to Woodhill Prison, Milton Keynes, were raised in the Ministry of Justice (MoJ) in December.

The Justice Secretary has said the first he heard of the matter was at the weekend, despite Tory claims that they brought it to the attention of Number 10 in December.

Downing Street has also denied any knowledge of shadow home secretary David Davis's letter.

But an MoJ spokeswoman said: "Ministry of Justice officials became aware in December of issues concerning visits to Woodhill Prison by Sadiq Khan MP."

Mr Davis questioned why ministers had not been informed. "After the lame excuse from Number 10, it is now becoming apparent that the Government did know about this very serious issue - at the time I wrote my letter," he said.

"It is beyond belief that the department would not flag up to a minister that the Wilson Doctrine had been broken within the department.

"It now appears that Mr Straw is in as little control of his department as the Home Secretary is of hers."

The development came as Mr Straw faced calls to extend an inquiry into claims that Mr Khan was bugged to wider concerns about covert surveillance in prisons.

Chief Surveillance Commissioner Sir Christopher Rose has been asked to establish whether conversations between the Muslim MP and an inmate of Woodhill were intercepted.

But the case has led to new fears that prison inmates' conversations with their solicitors are routinely monitored.