The center-left challenger to German Chancellor Angela Merkel in next year's elections, former finance minister Peer Steinbrueck, on Friday fended off criticism of his lucrative earnings from speeches, books and company boards.
The nomination of the 65-year-old Social Democrat (SPD) has prompted a slew of criticism of his high earnings outside the Bundestag (lower house) from Merkel's center-right coalition but also from the SPD's left wing and from anti-graft campaigners.
"This is really about attempts by some of my critics to damage my personal credibility. But it won't work," Steinbrueck, whose nomination was confirmed on Monday, told Die Welt daily.
Conservative lawmakers say his case underlines the need for new rules on politicians reporting their earnings, a call echoed by anti-graft group Transparency International. "We need a debate about transparency in (MPs') supplementary earnings," its German campaigner Christian Humborg told Reuters.
Bavaria's conservative state finance minister Markus Soeder said Steinbrueck's work in the financial sector undermined his promise of tougher rules for German banks.
The fuss could undermine Steinbrueck's bid to woo the left wing of the SPD, which mistrusts his centrist views on economics, such as advocacy of an increase in the retirement age. SPD left-winger Klaus Barthel urged him to "set an example" and publish his earnings.
Germans demand high standards of transparency from their elected officials, as witnessed by head of state Christian Wulff who had to resign this year over his murky personal finances.
"All groups in parliament agree we need more transparency on supplementary income," said Michael Grosse-Broemer, a leader of Merkel's conservatives in the Bundestag.
"It's not just a question of the law but of form," said his colleague Rainer Bruederle, parliamentary leader of the Free Democrats (FDP), Merkel's center-right coalition partners.
The conservative business daily Handelsblatt described Steinbrueck's earnings as a "record" for an MP.
As soon as he was nominated, Steinbrueck announced he would quit the board of steel giant ThyssenKrupp and all outside work, though not an unpaid seat on soccer club Borussia Dortmund's board where he saw no conflict of interest.
All of his paid engagements and contracts are listed by the Bundestag like other MPs, but the exact remuneration is not given, only which of three earnings bands each job falls into.
These bands range from 1,000 euros to 7,001 euros or higher, so there is no way of telling exactly how much an MP has earned.
In Steinbrueck's case, the seat on ThyssenKrupp's board and all but four of the other 85 appointments and engagements listed for the current parliament from 2009 fall in the top category - meaning earnings in excess of 560,000 euros in that period.
Conservative whip Grosse-Broemer said he wanted six earnings bands instead, with the highest encompassing income in six figures.
Steinbrueck told Die Welt he was completely focused on ousting Merkel.
"My job now for the SPD is to take this opportunity to beat Merkel's coalition. That is worth more to me than everything else," Steinbrueck said.
His nomination is seen as a worrying development for Merkel. His quick wit and solid credentials - as a minister in Merkel's 2005-09 "grand coalition" with the SPD he led Germany's response to the global financial crisis - could help him poach centrist voters from her conservative camp.
He has vowed never again to serve in a Merkel cabinet and support for his party, which suffered in the coalition, has risen since his selection, though he still lags well behind the chancellor.
(Additional reporting by Annika Breidthardt, Chris Cottrell and Thorsten Severin; Writing by Stephen Brown; Editing by Gareth Jones and Andrew Roche)