His comments have been taken to reveal dissent within his Social Democratic Party (SPD), less than two months before the election.
Steinbrück told the Frankfurter Rundschau newspaper, “I have serious doubts whether that [law] sends the right signal to the next generation.”
Steinbrück's party colleague, Labour Minister Olaf Scholz made the initial pensions promise in April and the relevant law was passed last month, with the pensions rate promise confirmed by the upper house of parliament on Friday.
The current generation of pensioners are doing, “better than ever before,” said Steinbrück. He said that others are worrying about the security of their jobs, while, “during the crisis, pensions are rising as they haven't done for three or four years.”
The SPD, which sees itself as Germany's party of social justice, scrambled to try to ensure his comments were not taken as a threat to the pensions promise – nor taken badly by older voters.
Steinbrück said was not challenging the pensions guarantee, but said, “Those who are pinched are the 25- to 35-year-olds who want to start families. We must take more care of this generation.”
Scholz' office said that the pension promise was passed unanimously by the cabinet, and added that Steinbrück's comments were not being taken as criticism.
The promise was not likely to be necessary anyhow, a spokesman said, as there was no reason to think that wage levels were likely to go down.
Steinbrück's spokesman later added that he was not distancing himself from pensions promise but had wanted to point out the burden it could place on the younger generation.
Christian Democratic pension expert Jen Spahn, who had opposed the pensions promise when it was first made, said he welcomed Steinbrück's comments. “I only have wish they had been made earlier and louder and in the cabinet meeting,” he said.