It takes almost five years on average from the opening of a formal investigation for a case to arrive at the crown court, according to the SFO's annual report today. The trial proceedings are then often subject to further delays.

"It's a very worrying trend," said Robert Wardle, SFO director. "We have had real difficulties, with the growing size of cases, the amount of material involved, especially computer material, and with the time required to obtain evidence from overseas." He hopes that Jessica de Grazia, the former US senior prosecutor he has hired as an adviser, will find ways to cut through the traditional and cumbersome British legal procedures. "We have to produce a huge great mass of material. Before we can charge we have to follow up all possible lines of inquiry, review all the material, produce full witness statements, and only then can we whittle it down to see what the real issues are."

He dreams of the day when quick "deals" with potential defendants are on offer, juries are dispensed with in complex cases, enough police support is available, and British corruption law is reformed along the lines of the much tougher US foreign corrupt practices act.

At the end of a bruising year for the SFO, Mr Wardle faces more urgent problems. There is a real possibility that a cabinet office review will fold the SFO, along with other prosecution agencies, into the new Ministry of Justice, while detaching him from the increasingly controversial superintendence of the attorney general.

This represents more than the usual game of Whitehall musical chairs, legal sources say. If a small department like the SFO has to compete for its budget with the demands of prisons, for example, it may lose out. Without a ring-fenced budget, the prosecutors will find their independence even further in danger.

SFO independence is a sore point. Wardle took on the thankless task of trying to prosecute firms for overseas bribery cases, though he admits: "The law is not really fit for purpose."

The 2001 anti-bribery legislation, which was forced on Britain largely by international pressure, has so far proved unable to be used for a single prosecution. The full-scale modernisation of corruption statutes, repeatedly promised to a restive Organisation of Economic Cooperation and Development, is languishing in the long grass of the Law Commission.

Mr Wardle ran into protest at the beginning of this year when he bowed to what critics see as political bullying from ministers. The career prosecutor had doggedly forced through compulsory production orders on BAE and its bankers, against the protests of their lawyers Allen & Overy and heavy pressure from the arms group's influential political supporters.

He was then made to halt a ?2m investigation into BAE's alleged secret arms deal payments to the Saudi royal family and their intermediaries, on "national security" grounds. This came just as he had managed to persuade the Swiss to open up bank accounts into which BAE had, it is alleged, paid more than ?1bn.

Wardle faces a judicial review from anti-corruption campaigners into his decision, and the embarrassment that the US has launched a Saudi investigation and is serving requests on him for documents.

Mr Wardle insists that he did the right thing in halting the inquiry, and that he sought to preserve the independence of the SFO from party politics by making the decision himself, rather than on instructions from Labour's attorney general.

He accepts the SFO was damaged by what happened, and there are those in the SFO who say that, having taken the painful decision on himself in order to protect the organisation's independence, Mr Wardle was "furious" to be contradicted by Tony Blair, who told reporters that it was he who had ensured the case was dropped, by informing Wardle that "British lives" would be at risk if it continued.

Wardle's contract, as determined by the last attorney general, runs out next April. But there is now a new attorney, Lady Scotland, and a new prime minister. Whitehall sources say it remains to be seen whether Wardle can restore confidence in the capacity of his struggling organisation to strike fear into fraudsters.