* SFO charges Barclays and four former top executives
* Comes weeks after ruling party pledged to abolish agency
LONDON, June 20 (Reuters) - Britain's Serious Fraud Office has defied critics who accuse it of failing to pursue top executives by criminally charging Barclays and four former senior managers, a month after the government pledged to abolish the crime-fighting agency.
Prime Minister Theresa May's ruling Conservatives pledged in the election manifesto to fold the independent investigator and prosecutor into the broader National Crime Agency to "strengthen Britain's response to white-collar crime".
That proposal drew criticism from lawyers and anti-corruption group Transparency International, which called it an "ill-conceived manifesto one-liner" and said the SFO had enjoyed increasing success in recent years.
The fraud charges brought by the agency on Tuesday were over undisclosed Barclays payments to Qatari investors during emergency fundraisings in 2008 that saved the bank from a state bailout.
"Taking on Barclays, one of the largest banks in the world, and its most senior officials who literally were at the very top, sends a very strong message that the SFO is now fearless in terms of the companies and individuals it pursues," said Sarah Wallace, a partner at law firm Irwin Mitchell.
The U.S. Department of Justice has long had a tougher reputation for pursuing multinational companies and individuals to face justice in the United States, often targeting wrongdoing outside its borders.
In contrast the SFO, which has a tight annual budget of around 35 million pounds ($44 million) and has to request extra funding from the government for its top cases, has been often criticised by lawmakers over its efforts to bring companies and senior individuals to book.
Some lawyers have also criticised the agency for prosecuting junior traders in its high-profile investigations into the manipulation of Libor benchmark interest rates - although SFO head David Green has said the agency merely follows the evidence.
The Barclays prosecution could buy the agency more time, said Michael Potts, a lawyer at Byrne and Partners.
"It certainly may make it more difficult for the government to abolish the SFO at a time when they are spearheading such a high-profile case," he added.
"Many will be surprised that they (the SFO) have sought to take on Barclays and no doubt an army of defence lawyers but it is indicative of a more emboldened SFO that they have sought to take on such a high-profile and possibly difficult case."
A spokeswoman for the Cabinet Office, which supports the Prime Minister and is responsible for the day-to-day running of the government, declined to comment when asked whether the Barclays charges had altered May's plans for the SFO.
The government's Queen's Speech, in which it traditionally spells out legislative programme, has been delayed after May lost her parliamentary majority in a June 8 election. It is now due on Wednesday.
'BETTING THE FARM'
Green, who is due to step down next April after a six-year stint running the SFO, was forced in 2015 to scrap his first corporate prosecution - that of Olympus Corp over a $1.7 billion accounting scandal - because judges ruled the SFO's criminal charge could not be brought against a company.
The corruption trial of British Canadian businessman Victor Dahdaleh collapsed in 2013 and the acquittal of eight former bankers over the last 15 months, charged with manipulating Libor, also dealt a blow to the agency.
But a series of recent deferred prosecution agreements (DPAs) with companies such as retailer Tesco and engineering group Rolls-Royce, and combined fines of around 630 million pounds, have been welcomed in parliament.
Some lawyers are questioning if it is in the public interest to prosecute a bank over conduct a decade ago, leaving current shareholders and employees to pick up the tab.
"Who does it punish and what purpose does it serve?" asked Jonathan Pickworth, partner at law firm White & Case.
But Green has talked tough throughout the five-year Barclays investigation.
Barclays was not offered a DPA, a deal under which a company can be fined but avoids criminal prosecution if a judge agrees the terms are fair and the interests of justice served. Green has repeatedly stressed that companies need to fully cooperate with investigators to qualify.
The bank locked horns with investigators over documentary evidence that it argued was protected by legal professional privilege, before deciding to relinquish the cache. This, lawyers say, is likely to have cost it a settlement.
Professional legal privilege ensures the advice lawyers give clients remains confidential.
The SFO's challenge now will be to show they can bring a tricky case to trial.
"David Green accepted in 2012 that the SFO would be judged on the performance of its Libor prosecutions. The SFO now seems to be betting the farm and possibly its future on a highly complex and very prominent prosecution of Barclays," said Ben Rose, a lawyer at Hickman and Rose.
($1 = 0.7890 pounds) (Reporting by Kirstin Ridley; Editing by Pravin Char)