Fraud investigators were accused yesterday of letting their budgets slide “out of control” after asking ministers for an extra £15 million, the second request in two months.

The extra funds are equivalent to about 40 per cent of the Serious Fraud Office’s (SFO) annual budget.

In a written statement, Baroness Scotland, QC, the Attorney-General, said that £10 million was being handed over to meet “urgent” spending needs at the SFO.

She added: “Parliamentary approval for additional resources of £15.45 million will be sought in the Spring Supplementary Estimate for the Serious Fraud Office.

“Pending that approval, urgent expenditure estimated at £10 million will be met by repayable cash advances from the Contingencies Fund.”

The Attorney-General’s office said that the money was for “major cases being prosecuted as well as some operational costs”.

The organisation has been criticised for spending heavily on legal advice to defend its dropping of the probe into BAE Systems' al-Yamamah arms deal.

It has also been investigating the role of bankers in the credit crunch, and the UK dealings of Bernard Madoff.

In November it was disclosed that the SFO had requested an extra £3 million on top of the £40 million previously budgeted.

David Howarth, Liberal Democrat justice spokesman, said: “This is the second time in as many months that the SFO has had to go cap in hand to the Government.

“It seems clear that its spending, like that of the Ministry of Justice, is out of control.

“Given its failure to investigate the most serious cases of international corruption, such as the BAE Systems bribery scandal, one has to ask exactly where this money is going.

“Government departments charged with the implementation of justice are consistently overspending but failing to deliver.”

An SFO official said that because of a delay in its normal funding arrangements the extra cash had been agreed.

"The Serious Fraud Office is funded in a different way to most Government Departments," she said.

“It receives additional funding annually to pursue large-scale fraud cases. This additional funding is the anticipated and agreed amount for this financial year.

"The Contingency Fund can be used to advance pre-agreed funds should they be required by a certain time."

She added that although the SFO had agreement for the necessary funding for its “blockbuster” cases, it did not receive formal parliamentary approval to use the money until part way through the year.

Normally, approval came through in auturmn but it had been delayed until the the spring, and formal approval would therefore not come through until March.

As a consequence, the SFO cash would run out before it received formal approval to draw down the blockbuster funding and it had therefore been granted money from the Contingency Fund.

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