BERLIN: The leader of Chancellor Angela Merkel's conservatives sharply criticised attempts by the Social Democrats (SPD) to push their ruling coalition to the left, accusing her partners of thinking of themselves more than Germany.
The two parties will decide in the next few weeks whether the centrist alliance has a future after the SPD chose a more leftist leadership duo, who have demanded new policies on climate, investment and the minimum wage.
Annegret Kramp-Karrenbauer, a Merkel protege and head of her conservative Christian Democrats (CDU), attacked the SPD for failing to make clear its commitment to the coalition, though she stopped short of ruling out all their demands.
"Just like you can't be a little bit pregnant, you can't rule a little bit," she told Bild am Sonntag, adding that the CDU remains true to the coalition deal and she expects the same of the SPD.
"It's bad for Germany if every important decision depends on the SPD's inner feelings," she told the weekly. "This coalition is for the country, not trauma therapy for ruling parties."
Her comments, which echoed warnings from other senior conservatives, set the stage for a tense start to talks on the coalition.
A collapse of the 18-month-old alliance could result in a minority government or snap election, threatening instability in Europe's biggest economy at a time when the ecologist Greens are gaining support and far-right Alternative for Germany (AfD) are strong.
Merkel, who has led Europe's biggest economy for the past 14 years, has said she will not stand at the next election.
Investment is a potential area of conflict. The SPD's new leaders want to spend about 450 billion euros (US$497 billion) over 10 years on infrastructure, schools and in embracing the digital revolution - from wider broadband access to robots.
Though the party held back from insisting the government drop a commitment to achieving a balanced budget without incurring new debt, it has demanded a more flexible approach, which Kramp-Karrenbauer appeared to rule out.
"There is no point in making new debt," Kramp-Karrenbauer told the Frankfurter Allgemeine Sonntagszeitung.
"If there is too little investment, it is not due to a lack of money, it is because the money that there is flows too slowly."
Kramp-Karrenbauer also rejected the SPD's calls to increase the minimum wage, arguing that the matter had to be decided by an independent commission, not politicians.
On climate, she said she did not want to start all over again after the parties had agreed in September on a complex climate package that aims to ensure Germany will meet targets to reduce greenhouse gas emissions.
However, there may be some room for manoeuvre, not least because the Greens are blocking legislation in the upper house.
Markus Blume, General Secretary of Bavaria's conservatives, rejected any notion of the government embracing the SPD's ideas.
"An SPD on a leftist path will not lead to the German government following a leftist path," he told Welt am Sonntag.