The extra injection of funds will more than double the budget of the immigration and nationality directorate overnight in an attempt to kill off asylum as a politically damaging issue in the run-up to next year's general election.

In his leaked memo Tony Blair identified asylum as one of two "touchstone issues" on which the government was seen as being "soft".

A Home Office spokesman confirmed that the money to finance the programme, designed to bail out the asylum system by clearing a backlog of nearly 100,000 cases by next March, is part of the Treasury's comprehensive spending review. Full details of the review, which was outlined last week by the chancellor, Gordon Brown, have yet to be announced.

The £600m comes on top of the £400m a year over the next three years that was announced in the comprehensive spending review.

The massive scale of the rescue operation ordered by Mr Blair and Jack Straw shows the depths of the crisis facing Britain's asylum process.

A botched computerisation project and an ill-timed move of the directorate's headquarters led to one of the biggest bureaucratic breakdowns in the history of Whitehall.

At one point the number of decisions taken each month fell to 800 and the backlog soared from 50,960 in February 1998 to a peak of 104,000 earlier this year.

At the height of the crisis rotting case files were discovered dumped in a car park underneath the Croydon headquar ters of the immigration and nationality directorate.

A Home Office spokeswoman confirmed that large-scale recruitment campaigns were already under way to hire and train the extra staff needed.

It is thought that the overall number of staff is to increase from about 6,500 earlier this year to more than 11,000 over the next two years. Around 9,000 staff should be in place by next March.

"This year's budget is more than doubling. It was £590m and now it is going to be £1.2bn. By March 2001 we want to clear the backlog," she added. "We want to make between 130,000 and 150,000 decisions in this financial year. That covers the backlog of 90,000 cases and the number of new asylum applications we expect to get."

She said that two new targets were being set for the asylum system. The first was to ensure that by January next year that 70% of all new asylum claims had an initial decision within two months. The second was longer term and aimed for 75% of all asylum decisions to be taken within two months. A further four months is to be allowed for appeals.

It currently takes 13 months on average for an asylum case to be resolved.

The immigration minister, Barbara Roche, believes that the fact that new asylum applicants have gone to the back of a very long queue has been a major factor in the rise in numbers of asylum applicants to Britain and that quicker decisions will prove an effective deterrent.

As the speed of asylum decision-making is stepped up, so ministers expect the number of removals of failed asylum seekers to grow as well.

An extra £100m is being made available to build three new detention centres to ensure that those who face deportation do not disappear.

It is planned that the 8,000 removals carried out last year will rise to 12,000 in this financial year and reach 30,000 in 2001/2002.

Although stepping up the scale of removals is thought to be popular with former Tory voters, Home Office ministers are nervous that a single controversial case could suddenly undermine public support for such a programme.

Nick Hardwick, the chief executive of the Refugee Council, said news of the emergency money had come as a shock but he thought it could succeed. "The reason why they could not keep up with the backlog was because the cases are particularly complex or anything but because the files were put on shelves and left there for years and years," he said. "It is procedural delays and administrative chaos they have to deal with.