* Regulator names ex-UBS executive Mark Branson to top post
* Branson's past at UBS has stirred debate among lawmakers
* Branson given all-clear by FINMA in 2012 over Libor
* Forex rigging, U.S. tax probe among issues for regulator
* Branson plans to apply for Swiss citizenship (Adds comment from Branson at press briefing)
By Oliver Hirt and Katharina Bart
BERN/ZURICH, March 26 (Reuters) - The Swiss government named British-born former banker Mark Branson on Wednesday as the first non-Swiss national to head its financial regulator, just as the body probes currency markets and prepares for a major review of big banks.
Branson, 45, had worked at the regulator since 2010 and became deputy chief last year. He previously held a senior post at a division of UBS AG involved in the rigging of interest rates, for which the bank, among others in the industry, has paid huge fines.
"Because of his experience, and to ensure continuity, Mark Branson had been the top candidate from the outset", FINMA said in a statement which confirmed what two sources familiar with the matter had told Reuters on Tuesday.
Branson was in charge of UBS's Japan unit between 2006 and early 2008, when the bank has been found to be involved in rigging the London Interbank Offered Rate (Libor), a benchmark used to price trillions of dollars of financial products.
FINMA gave Branson, who was excused by the regulator from all UBS Libor matters in mid-2012, the all-clear over the fraud, on the basis that traders at UBS answered to investment banking leadership in London, not to Branson, who was never accused of any wrongdoing. Branson himself has not commented.
In December 2012, UBS agreed to pay roughly $1.5 billion to settle with U.S., UK and Swiss regulators over the Libor scandal. UBS's Japan unit pleaded guilty to criminal fraud.
Some former and current colleagues denied Branson's past would impede his role as head of FINMA.
"Mark Branson has a proven integrity and a professional objectivity ... He can be very close to someone but it doesn't compromise his objectivity," ex-UBS CEO Luqman Arnold said.
But criticism may resurface when Branson has to deal with future misconduct cases.
"There cannot be anything which questions the credibility of FINMA in any way. Branson's UBS past is a problem," Christophe Darbellay, president of Switzerland's Christian Democratic People's Party, which is part of the seven-party Swiss government, said before Tuesday's announcement.
FINMA, along with regulators in the United States, Britain and Asia, is probing possible manipulation of the $5.3 trillion-a-day foreign exchange market and Britain's financial watchdog has said allegations about currency markets are as serious as those concerning Libor.
Branson joined FINMA in 2010 to oversee Switzerland's banking sector and was named deputy chief executive last year. He has been acting CEO since January when Patrick Raaflaub announced his surprise departure.
Branson, who had also been criticized by politician Darbellay and others for not being Swiss, told journalists he isn't yet eligible to apply for citizenship in Switzerland, but planned to do so later this year, when he will have lived in the country for 12 years.
His promotion marks a continuation of Switzerland's tougher, hands-on approach to banking regulation forged in the aftermath of the 2008-09 global financial crisis.
Taxpayers had to prop up UBS with a 6 billion franc bailout after its disastrous bets on the U.S. mortgage market, since when Swiss authorities have imposed some of the world's toughest capital requirements on UBS and rival Credit Suisse.
Branson, a maths and management graduate from Cambridge University, defused any suspicions of favouritism towards UBS last year when he ordered it to stockpile 28 billion francs in extra capital, a sum later lowered to 22.5 billion but which still hit the bank's returns targets.
FINMA and the Swiss National Bank (SNB) begin a review next year of laws on banks regarded as being "too big to fail". This is being closely watched by investors, because of political calls in Switzerland for a tougher line on institutions that think their scale allows them to expect state bailouts.
An extensive U.S. probe into Swiss banks' role in helping wealthy U.S. citizens evade tax has also fundamentally altered the relationship between the regulator and the banks.
Bankers in Zurich, Geneva and Basel have complained that the regulator had "gone rogue" on them, after it urged banks to come clean about their role in offshore tax evasion and to take provisions for resultant penalties, or risk more costly prosecution by U.S. authorities.
Industry lobby group the Swiss Banking Association said it "expects the new CEO to establish again a spirit of trust and cooperation between the banking industry and the regulator".
Branson should be versed in dealing with crises. In 2001, as head of communications for UBS, he orchestrated its defence of its role in the bankruptcy of national carrier Swissair, which sparked widespread political and popular outrage.
In 2008, he became the public face of UBS in the United States, apologising in a dramatic hearing on Capitol Hill for the Swiss bank's role in helping Americans evade taxes.
People who have worked with Branson, who is fluent in French and German, say he is principled and a stickler for details. At UBS he insisted on proofing statements meant for investors word-for-word, marking each line with a tick. ($1 = 0.8862 Swiss Francs) (Additional reporting by Oliver Hirt; Editing by Anthony Barker and David Holmes)