Merkel’s conservatives agreed in their coalition deal with the centre-left Social Democrats (SPD) to reduce the retirement age to 63 for people who had paid into the social security system for 45 years.
The reform is being led by Labour Minister Andrea Nahles (SPD).
But the pension reforms are expected to cost an extra €4.4 billion a year, rising to an additional €11 billion a year by 2030 and have angered many conservatives.
Julia Klöckner, deputy chairwoman of the Christian Democratic Union (CDU), suggested on Monday that the reform may now not go ahead.
“Retirement at 63 is there as a compromise in the coalition agreement, but it doesn’t state that it has to follow the Nahles model,” Klöckner said referring to the Social Democrat labour minister.
She told the Saarbrücker Zeitung on Monday that if the SPD didn’t understand that then there would be no agreement on retiring at 63.
Under the SPD plans the 45 years of work needed to retire will also include periods of unemployment, something the CDU is opposed to.
The Rheinische Post said on Monday that crediting time spent unemployed to the 45 years would cost €700 million a year.
Economists have also criticized the plans, arguing it weakens the goal of slowly raising the retirement age in the fast-ageing country.
Under the reforms, pensions will also go up for mothers whose children were born before 1992, affecting around 10 million mothers.