(Adds details and background)
By Caroline Copley
ZURICH, March 20 (Reuters) - Swiss prosecutors have widened a probe over the leaking of private bank information that helped force the head of the Swiss National Bank Philipp Hildebrand to resign, to include a right-wing politician instrumental in his downfall.
Police searched the house and office of former cabinet minister Christoph Blocher on Tuesday, Zurich's state prosecutors said in a statement, on suspicion of violation of the country's strict bank secrecy laws.
Blocher's spokesman Livio Zanolari had no comment on the probe.
Hildebrand was forced to resign in January over a controversial currency trade made by his wife Kashya in August, weeks before the bank moved to stop the Swiss franc climbing.
The latest twist in the Hildebrand saga represents an embarrassing fall from grace for the 71-year-old Blocher, who is widely credited with transforming the Swiss People's Party (SVP) from a small, rural movement into Switzerland's biggest political force.
Blocher, a long-time critic of Hildebrand, had repeatedly called for his head after the SNB ran up big losses in 2010 from ill-fated interventions to try to stem the franc's rise.
Describing himself as a "postman" in the affair, Blocher has denied having seen any bank documents, which would contravene his party's staunch defence of bank secrecy. But the government said previously that Blocher had given it a copy of a statement from a Hildebrand bank account on Dec. 15.
Since his exit from government in 2007, Blocher has been a vocal critic of the government. He has led right-wing opposition to a U.S. tax proposal to reduce bank secrecy championed by the woman who replaced him in government, Eveline Widmer-Schlumpf, one of the staunchest defenders of Hildebrand before his resignation.
In January, prosecutors opened criminal proceedings into two members of Blocher's party, Hermann Lei and Claudio Schmid, who are both accused of passing on data on Hildebrand's account.
The affair shone the spotlight on the SNB's credibility at a time when the central bank is trying to defend a cap of 1.20 francs to the euro.
Last week a special parliamentary session on the currency trading scandal rejected demands from the SVP to curb the independence of the SNB and its ability to cap the franc. :
Also on Tuesday, the International Monetary Fund called on Switzerland to allow its currency to start trading freely again once deflationary pressures ease and growth picks up. (Reporting By Katharina Bart and Caroline Copley; editing by Andrew Roche)