LONDON (Reuters) - Barclays said Jes Staley will be fined by British regulators for attempting to unmask a whistleblower, but will be able to keep his job as the bank's chief executive.

The country's banking watchdogs concluded Staley's attempt to find out who wrote a letter raising "concerns of a personal nature" about an unnamed senior employee represented a breach of individual conduct, Barclays said on Friday.

Staley's case is the first big test of Britain's "senior managers regime" (SMR), aimed at making top banking officials personally accountable for their actions after few were punished for their roles in bank collapses during the financial crisis.

If Staley accepts the findings of the regulators, it would be the first time that a sitting chief executive of a major bank in Britain has been fined by its regulators. A bank spokesman said the size of the fine had yet to be determined.

Barclays said the Financial Conduct Authority (FCA) and the Bank of England's Prudential Regulation Authority (PRA) were "not alleging that he (Staley) acted with a lack of integrity or that he lacks fitness and propriety to continue to perform his role as Group Chief Executive Officer".

News of the FCA and PRA fines follows a more than year-long probe in Britain that had led to speculation among some investors and bank insiders that Staley could have been forced to step down if deemed unfit to continue by those authorities.

Barclays also said that the FCA and PRA will not take enforcement action against the bank, while authorities in the United States are still investigating the case.

"Staley will live on to fight another day – which we welcome as a positive development for the bank and a relief for shareholders," John Cronin at Irish broker Goodbody said.

Barclays shares rose 0.5 percent by 0741 GMT, against a 0.8 percent rise in the FTSE 350 banks index <.FTNMX8350>.

"He’s been delivering on the strategy far more effectively than his predecessor had and therefore absent any sort of genuine malpractice we're pretty keen for him to crack on," one of the bank's top 40 investors said.

Activist investor Edward Bramson has taken a 5 percent stake in Barclays, piling pressure on Staley to fix low returns at its investment bank.

"While today's news is interesting, Bramson's presence and plans are still more important for the share price trajectory,” a second top-40 investor in Barclays said.

The British bank, which in April last year said it had reprimanded Staley and would cut his bonus for his attempts to identify the whistleblower, will be required to report to the FCA and PRA on aspects of their whistleblowing programmes.

The watchdogs could have banned Staley and opting for a fine could dent the fledgling SMR's credibility.

"The magnitude of banning the sitting CEO of such a systemically important institution made outcomes other than a fine unlikely, but the case does set an interesting precedent," said Nicholas Queree, an associate at law firm Peters & Peters.

DRAFT WARNINGS

Staley received the draft warning notice last week and was given 28 days to accept the findings or appeal. If he agrees to pay the two fines he would get a 30 percent discount.

The fines have been set according to a formula that considers the type of offense, the offender's position in the company, any financial hardship, any previous cases, and whether there was any monetary benefit from the offense.

"We ... will announce the outcome once this issue has reached a conclusion," the FCA and PRA said in a statement.

Legal experts question whether a light sanction for Staley could send a signal to other potential bank whistleblowers that they risk unmasking if they speak out.

Barclays said it will recommend Staley's re-election as a director at its board meeting on May 1. At the last annual meeting he faced resignation calls, but was given a public endorsement from Chairman John McFarlane.

Staley's pay package was 3.88 million pounds ($5.45 million) in 2017, 8.5 percent less than the previous year.

(Reporting by Lawrence White and Huw Jones, additional reporting by Emma Rumney, Simon Jessop and Maiya Keidan,; Editing by Silvia Aloisi and Alexander Smith)

By Lawrence White and Huw Jones