Vice Chancellor Philipp Rösler, of the pro-business Free Democrats (FDP), told the Bild am Sonntag newspaper that many of Merkel's party's key proposals for the coming year were unfeasible. Come early November, the two groups will sit down to try to agree on a number of topics.
This could prove tricky, as there has been friction between the FDP and their larger coalition partners the Christian Democratic Union (CDU) and its Bavarian sister party the Christian Social Union (CSU).
“The coalition has to improve its outward appearance,” said the CDU parliamentary party leader Volker Kauder in an attempt to pull everyone into line, just a year before the next general election.
But Rösler was clear in saying that he opposed giving working grandparents time off to care for new grandchildren, pension subsidies and paying parents who keep their children at home, instead of sending them to day-care - because all these proposals would cost too much money.
The 39-year-old cited slow economic growth and a strained budget as reasons for his rejection of the proposals. Instead, the government should concentrate on strengthening the country's economy and creating jobs, he said.
Rösler has also voiced concern about the CSU moving to change the rules for refugees coming to Germany from the former Yugoslavia. Currently, people coming from Serbia and Macedonia do not need visas and the Bavarian conservatives want to impose visa requirements again in an attempt to stop people coming to the country.
Instead Rösler would push for a reduction in electricity taxes and the abolishment of the €10 doctor's fee, said the paper.
Despite criticism from within his own party and poor performance in polls, Rösler said he had no intention of changing his position before next autumn's election.
“The FDP has demonstrated many times in 2012, that with good politics and trustworthy members, it would win an election,” he said.