Angela Merkel, the German chancellor, on Monday warned her Social Democratic allies not to try to roll back recent economic reforms as she reasserted her authority over her unruly grand coalition.

"The coalition has made important achievements in respect to job creation and the consolidation of government finances. Under my leadership the coalition will not do anything to threaten these achievements," she said.

She was speaking after her Christian Democratic party used coalition talks on Sunday evening to force the SPD into compromises on minimum wages and on a subsidy for commuters - two symbolically important issues for the centre-left party.

Ms Merkel said she expected agreements on issues dividing the two parties at the next meeting of the CDU-led coalition on November 12. Tensions between the two sides have increased recently, especially following an SPD congress last month that called on Ms Merkel to reverse elements of the Agenda 2010 reform programme introduced by the SPD's Gerhard Schröder, the former chancellor.

Kurt Beck, SPD chairman, on Monday acknowledged it was important to return to "working in a business-like way" in the CDU-led coalition, following a string of recent speeches in which he attacked the chancellor's party and said Germans had "had enough" of economic reforms.

The coalition partners agreed in principle on Sunday on a minimum wage of €8-€9.80 an hour for postal staff, but the number of the employees covered is likely to be smaller than the SPD had hoped for.

Mr Beck's party, which for months has campaigned for minimum wages as a means of boosting its flagging poll ratings, had hoped that most of Germany's estimated 312,000 postal workers would be covered. Under the complicated formula agreed on Sunday, many fewer are now expected to be covered, with tens of thousands of part-time post delivery workers being excluded.

The coalition agreed not to reintroduce a €2.5bn (£1.7bn, $3.6bn) subsidy for commuters abolished in January, despite recent pressure from some SPD leaders to revive the popular tax break.

Several court rulings have questioned the legality of the abolition move, but the coalition agreed no changes would be made until the constitutional court next year made a ruling on the topic.

On this issue Peer Steinbrück, finance minister and a leading reform-minded SPD politician, sided with Ms Merkel in arguing against his own party's populist instincts, officials said.

In a further blow to the SPD, Ronald Pofalla, CDU general secretary, said another recent proposal by Mr Beck - extra unemployment benefits for elderly jobseekers - could also falter.

While the CDU in principle backs Mr Beck's proposal, it insists that the extra expenditure must be compensated for with cuts in other jobless benefits, a position not shared by the SPD.