The lashing comes as the Chancellor promised to deliver a “stable government” after breaking four months of political deadlock to agree a coalition between her Christian Democratic Union (CDU) and the Social Democrats (SPD).
The deadlock prompted speculation the 63-year-old German leader could be forced to step down, but after long negotiations over key issues such as foreign policies, immigration and the environment, Ms Merkel will remain Chancellor for her fourth term.
The SDP, which won 59 seats in the September 2017 federal election, has now been accused of being “the biggest losers” which have “ended up as the German government’s de facto leaders”.
Josef Joffe, a member of the editorial council of Die Zeit in Hamburg, called Ms Merkel’s decision to hand SDP critical cabinet posts such as foreign ministries, family and labour as “anything to stay in power”.
Writing for Politico, he said: “Merkel has yielded critical levers in order to buy herself another four years in the country’s top office.
“Now these SPD politicos, most of whom are relatively unknown outside Berlin, will be the ones to shape the politics of Europe and Germany, the EU’s mightiest member, in the years to come.”
SDP leader Martin Schulz, who is the former European Parliament president, has styled the coalition agreement as “an end of forced austerity”.
The pitch is designed to appeal to his party’s 464,000 members before they vote on the deal, which is the final hurdle the SPD needs to pass before the government can be formed.
Mr Joffe added the election last year was a “popular vote of no-confidence” after losing supporters to the Alternative for Germany (AfD) following years of political turmoil after Europe’s migration crisis in 2015, insisting it is now a “cosmic joke” the two parties are joining forces.
Ms Merkel is widely-considered to be one of the key-consensus builders in the European Union, seeking to push major reforms which would see greater unification of the continent.
But she was slammed for “winning this race of losers”.
Mr Joffe wrote: “This masterful politico, who has outmanoeuvred every potential contender for 12 years, could only hang on to power by practically giving away the government to her weakened junior partner.”
The deal was welcomed by the EU, with the president of the European Council Donald Tusk hailing the agreement as “good news”.
But the elevation of Mr Schulz, who was made foreign secretary, will see even stronger ties between Berlin and the EU, peddling the need for a United States of Europe.