The German chancellor finally reached an agreement with Martin Schulz’s SPD group this month as she attempts to claw back power after failing to form a government in Germany’s general election. 

But with party delegates expected to vote on the agreement on Sunday at a conference in Bonn, members in the SPD heartland have raised concerns a grand coalition will force them to lose their voice.

Critics from SPD claim a coalition with Angela Merkel’s Christian Democrats (CDU) and their Bavarian sister party, the CSU, willt see them give in and receive little in return after four painful years in the previous grand partnership. 

Rainer Brinkmann, head of the local SPD office told politics news site, Politico.co.uk: “In effect, we’ve already had four years of coalition negotiations - that is, four years in a grand coalition. 

“I’d hoped we would get a bit more from the CDU/CSU.. personally, I don’t consider this result sufficient.” 

Discussing the coalition blueprint during a meeting in Dortmund for local SPD members, Ulrich Piechota, the group’s leader, said: “There are some points where I say great, very nice. 

“There are many others where I say ‘this can’t be the SPD’. 

“If we go into another grand coalition, what happens in four years. 

“Will we stand here then with 15, 16, 17, 18 percent? With the same situation, we’ll keep disappearing.”

Simone Weiß, another member, added: “We always talk about how we’ve lost our profile. 

“We have great ideas, but we can’t implement them with a grand coalition.”

Meanwhile, other SPD members are considering rejecting the coalition deal in favour of a minority government. 

Alisa Löffler, a Dortmund city council member and SPD delegate, added: ““We need to make it clear that we’re not the ones with the responsibility. 

“Now is the time when the CDU/CSU needs to come up with alternatives.”

If a deal is rejected, the EU will watch on nervously as their de facto leader struggles to regain control within her own country, long considered the economic powerhouse of Brussels. 

There is still a way to go before the new coalition can be confirmed and leading movements of the SDP have vowed to press for improvements to the blueprint agreed at the end of last week.

SPD party delegates will vote on Sunday on whether or not to progress to formal talks with Ms Merkel’s Christian Democrats (CDU) and their Bavarian sister party, the CSU, based on the position paper drawn up during exploratory talks.

If the SPD votes against the deal it will spell disaster for leader Martin Schulz, who will almost certainly be expected to resign after rowing back on a campaign pledge not to enter a coalition government with the CDU.