By Stephen Brown
BERLIN (Reuters) - German Social Democrat Peer Steinbrueck's hopes of becoming the centre-left challenger to Angela Merkel in next year's elections have hit a bump with revelations that he used his former post as finance minister to seek sponsorship for a chess event.
Chess fan Steinbrueck used ministerial stationery to write to the partly state-owned post office and telecoms firms seeking support for an exhibition match in 2006, when he was a minister in a 'grand coalition' of Merkel's conservatives and the SPD.
The match between Russian grandmaster Vladimir Kramnik and the chess-playing computer "Deep Fritz" took place in Bonn.
The 65-year-old politician told the top-selling daily Bild - which ran pictures of the letters on Finance Ministry stationery - that he had acted purely "in the interests of the wider chess community. I see nothing scandalous in it".
"It's unlikely (Deutsche) Telekom or (Deutsche) Post felt pressured - they ended up deciding against sponsorship," he told Monday's edition of the paper, which headlined its story "Will a letterhead affair check-mate him?".
Merkel's spokesman Steffen Seibert, asked if there were any rules about cabinet ministers using official stationery to seek such sponsorship, said: "Basically, the ministerial letterhead should be used for correspondence related to official business."
Steinbrueck is one of three contenders to lead the SPD's bid to unseat Merkel in 2013. The others are former foreign minister Frank-Walter Steinmeier and party chairman Sigmar Gabriel, who is hesitating because of low popularity ratings and a new baby.
The SPD has said it is likely to wait until after a state election in Lower Saxony in January to name its candidate, but pressure is rising to decide sooner.
Steinmeier launched a feisty attack against Merkel at a party meeting nine days ago, boosting expectations that he would be the SPD's man.
But Steinbrueck seems reluctant to bow out. This week he will unveil a series of financial policy proposals including plans to force banks to separate investment banking from their traditional retail and lending operations.
Steinbrueck has the backing of two former SPD chancellors, Helmut Schmidt and Gerhard Schroeder, but is distrusted by the party's left wing because of his centrist economic views. As finance minister in 2005-2009, he led the German response to the financial crisis in characteristically combative style.
The SPD's support for Merkel in the euro zone crisis makes it tough for the party to differentiate itself ahead of the vote in a year's time, especially as she has espoused centre-left ideas such as shutting down nuclear power and a minimum wage.
Another "grand coalition" of conservatives and the SPD looks possible, although the SPD would prefer to form a coalition with the Greens. Together the two leftist parties score just over 40 percent in polls, level with Merkel and her struggling current coalition partners, the Free Democrats.
(Reporting by Stephen Brown; Editing by Kevin Liffey)