Metropolitan Police Commissioner Sir Paul Condon has also made an attack on police funding, claiming lack of cash had seen his force lose more than 2,000 officers during his time in charge.

Mr Straw has been embroiled in controversy since telling the Labour party conference he would provide cash to recruit 5,000 extra officers, over and above existing hiring plans.

A leaked Treasury memo warned him the net effect of this would be to keep total police levels constant - contrary to the impression given by his announcement that officer levels would rise.

But in a parliamentary written answer released on Thursday night, Mr Straw said the total "wastage rate" - officers resigning, retiring or being dismissed - across England and Wales was 5,343 in 1996/97, 5,885 in 1997/98 and 5,569 in 1998/99, a total of 16,797.

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Police forces are already planning to recruit 11,000 officers over the next three years - which together with the 5,000 announced by Mr Straw would make a total of 16,000.

But if current trends continue, the 16,000 new recruits would not replace the almost 17,000 who leave over that period - leading to a net fall in police numbers.

Shadow home secretary Ann Widdecombe said: "This substantiates what we have been saying, which is that the rate of recruitment, even with the 5,000 officers, is not going to keep pace with the numbers leaving.

"In other words, there will be another fall in police numbers and that has been thoroughly rumbled by his own figures."

'Fundamentally flawed funding'

Sir Paul criticised the "fundamentally flawed" funding system had hit his force hard.

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He told Mr Straw at an meeting of rank-and-file officers that the current system of financing forces could not continue and had affected murder inquiries in the capital.

Speaking at a Metropolitan Police Federation meeting, Sir Paul said when he took over the force seven years ago, the Met had 28,400 officers but when he leaves in January there will be only 26,200.

Sir Paul said his force had emerged badly from the national funding formula and told Mr Straw: "This cannot go on.

"It means we cannot devote the resources to murder inquiries that other forces do. It means we have fewer bobbies on the beat than we or the public would like."

Mr Straw, speaking at the same meeting, stood by his pledge, insisting it represented "new money" to recruit extra manpower.

But he said he could not predict how many police officers there would be at the end of the three years of extra funding, because home secretaries no longer had the power to set police force numbers.

"What I can say, and this is what makes our pledge different, is that all of our new money will be ringfenced so that chief officers can only spend it on new officers who they would not otherwise have recruited."