PORTER GOSS, the Director of the CIA, unexpectedly resigned last night without any official reason, after less than two years in the job.

Senior White House officials said that Mr Goss, a President Bush loyalist who was the first sitting member of Congress to be appointed to the post, had left by “mutual consent”. That explanation, and the timing of the announcement made by Mr Bush on a day on which he and his Administration had been touting good economic figures, left analysts on both sides of the political divide unclear about the reason for his abrupt departure, particularly as no successor appeared to have been lined up.

The resignation caught officials by surprise and plunged the world’s biggest spy agency into new uncertainty as it seeks to recover from the intelligence blunders that preceded the terrorist attacks of September 11, 2001, and the Iraq conflict.

Six months before difficult mid-term elections for Republicans, the move also appeared politically unfavourable to Mr Bush. Mr Goss’s successor will face Senate confirmation, giving Democrats another chance to rehash their allegations that pre-war intelligence was manipulated and exaggerated.

In recent days the CIA has come under an ethics cloud after its No 3 official, Kyle “Dusty” Foggo, became the subject of the FBI’s investigation into Randy “Duke” Cunningham, the former Republican congressman who was jailed this year for taking bribes from defence contractors.

FBI officials said this week that they were looking into allegations that one of the defence contractors provided Cunningham with prostitutes in Washington hotel suites.

Mr Foggo, an old friend of Mr Goss, admitted this week that he had attended poker games arranged by the defence contractor in Washington hotels, but that he had engaged in no improper conduct.

Bob Barr, a former congressman, suggested that the scandal might prove the key. “I think there’s going to be more coming out. It’s starting to reach into the CIA,” he said.

Mr Goss, a veteran Republican congressman and chairman of the House Intelligence Committee when he was appointed, took charge of the CIA after the resignation of George Tenet, who had been accused of intelligence failures leading up to the 9/11 attacks and the invasion of Iraq.

Since his appointment Mr Goss has seen the profile and responsibility of the CIA director diminished after the creation of a new intelligence czar — the Director of National Intelligence (DNI) — who oversees all 15 intelligence bodies.

It is the DNI, John Negroponte, and not Mr Goss, who gives Mr Bush his daily intelligence briefing, a job previously the responsibility of the CIA chief.

It is understood that Mr Goss and Mr Negroponte have had serious disputes in recent weeks. Mr Goss was known to be unhappy with his loss of status, and he has had a troubled tenure. Much of the CIA has almost been at open war with the Bush White House since the invasion of Iraq, and one of Mr Goss’s main jobs was to stop leaks from within the agency and improve relations with the Administration.

But he has been met with resignations of veteran CIA officials and dissatisfaction in the middle ranks.

“I believe the agency is on a very even keel, sailing well,” Mr Goss said after Mr Bush said that he had accepted his resignation.

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