Chancellor Angela Merkel's main challenger in Germany's general election next year, Peer Steinbrück, on Monday called for much stricter regulation of Europe’s banks and a curbing of their power.

He also reiterated remarks criticizing the tax evasion agreement between Germany and Switzerland as insufficient. Steinbrück said he would steer his Social Democrat Party (SPD) to vote against a Merkel-backed proposal to protect Swiss banking secrecy on the condition that Germany receive billions from citizens suspected of tax fraud.

The deal between Switzerland and Germany was intended to come into force next year but Merkel lacks a sufficient majority in the German parliament's upper house, the Bundesrat, to pass the legislation.Steinbrück's oppositional stance on a deal with Switzerland has previously prompted strong rebukes from the German neighbor and tax haven.

Watch video 01:21 Steinbrück to Challenge Merkel

Steinbruck also came out in strong support of the introduction of a legally binding minimum wage across Germany, an idea the conservative ruling coalition has been avoiding.

Steinbrück for chancellor?

The SPD figurehead's remarks were made at a joint press conference with party chairman Sigmar Gabriel, who explained that the partly leadership was backing Steinbrück’s candidacy unanimously.

The next step will be official nomination by the party’s rank and file at an SPD conference in December.Steinbrück stressed on Monday that he intended to win over disgruntled voters from Merkel's Christian Democrat CDU and her coalition partner, the liberal FDP.

Steinbrück's SPD party is behind Merkel's CDU in the polls

Latest opinion polls meanwhile indicate that he is facing an uphill battle. Angela Merkel’s party has a strong lead in the polls one year before general elections. The Social Democrats, who are pinning their hopes on forming a coalition with the opposition Greens to rule, are trailing by about 6 percentage points.

The 65-year-old politician, who belongs to the Social Democrats’ centrist wing, served as a finance minister in a coalition government under Chancellor Angela Merkel for four years until 2009. He was state premier of Germany’s most populous state, North Rhine-Westphalia. There, he fought his only election as top candidate for the state as incumbent - and lost.

rg, sej/msh (Reuters, dpa, AP)