Tim Jones: Gordon Brown returned today to start the search for a new Press Secretary

Gordon Brown should stop his spokesman having access to Treasury documents and enforce a "quarantine" period before he takes a private sector job, they say.

Mr Brown returned to work at the Treasury on Tuesday morning to find his friend and press secretary still at his desk.

BBC Political Editor Robin Oakley: "We've seen evidence of civil war in the government"

Mr Whelan on Monday became the third victim of the loan scandal which cost former Trade Secretary Peter Mandelson and former Paymaster General Geoffrey Robinson their jobs.

The spokesman chose to quit after weeks of speculation he was behind the revelation Mr Mandelson borrowed £373,000 from millionaire Mr Robinson to buy a house.

Charlie Whelan will quit at an "appropriate opportunity"

But he said he would leave only when an "appropriate opportunity" became available.

The opposition are calling for a good deal of time to elapse before Mr Whelan takes a new job, especially if it is in the City.

Conservative Party Chairman Michael Ancram said Mr Whelan should not see any more Treasury papers, particularly those relating to the Budget.

Mr Ancram has written to Cabinet Secretary Sir Richard Wilson saying Mr Whelan should not be allowed to take a job in the City without a "quarantine" period.

Michael Ancram: "Whelan must go now"

He said: "I asked the Cabinet secretary to reassure us that the normal rules of a three-month gap, seeking approval from the Cabinet secretary himself to take a job, would be applied."

But Mr Whelan's rank means he will only have to get the Treasury permanent secretary's approval before taking a new job.

Michael Ancram: "This is bad for the integrity of the government"

Questions have also been asked about where Mr Brown was on Monday - the day when the euro started trading on financial markets in London, as well as the resignation of his controversial aide.

A Treasury spokesman said the Chancellor was working in his Dunfermline East constituency, but reporters failed to track him down.

He made no public comment on the loss of his most trusted aide.

It is expected Mr Brown's new choice of spin doctor will be vetted by Number 10.

Mr Whelan was one of four key players in Labour's media team which helped win the 1997 general election.

Headed by Peter Mandelson, the spin doctors included Alastair Campbell, David Hill and Mr Whelan. Mr Campbell is the only one left in high office.

Mr Whelan is the Treasury's second casualty over the loan affair, following the loss of Mr Robinson, who was also a close colleague of the chancellor.

Mr Robinson's position had remained vacant for nearly two weeks until the appointment of Dawn Primarolo, another follower of Mr Brown.

The Mirror newspaper has claimed Mr Brown's elder brother John was behind the leaking of a letter Mr Mandelson wrote to the chancellor in opposition.

Mr Mandelson's aide Benjamin Wegg-Prosser told the paper the chancellor's brother had disclosed the letter in which Mr Mandelson plotted against Mr Brown in the race to lead the party following John Smith's death.