The party’s stance comes after the leader of the Social Democratic Party (SPD) Martin Schulz has said there should be a federal Europe by 2025.
The SPD leader Martin Schulz said: “We don’t have to govern at any price, but we must not reject governing at all costs either.
“I want a Europe constitutional treaty that creates a federal Europe.”
Mr Schulz said a draft of the European Constitutional Treaty “must then be presented in all member states and those that do not agree would automatically leave the EU”.
The SPD leader said his party would gain support by providing a clear vision of Europe.
However, Volker Kauder, who is often referred to as the “right hand of Merkel” called the proposal “more of a threat to the EU and citizens’ approval of Europe”.
Mr Kauder said: “The proposal would also jeopardise the world of unification that is unique in the history of the world because the majority of member sates certainly wouldn’t participate in created a United States.
“I also wonder where the added value of this United States should be compared to today’s Europe.”
Chief of Staff of the German chancellory Peter Altmaier said: “The discussion of whether Europe should be a federal state, a confederation of states of the United States is one for scientists and journalists – not for German foreign policy.
“A United States of Europe would transfer member states’ sovereignty to Brussels and there would not be a majority for that in many EU states.”
Although the two German parties disagree on the future of Europe, Merkel’s party still hopes to form a coalition with Schulz’s Social Democrats by early next year.
According to a poll by the public broadcaster ARD, more than half of Germans are against another “grand coalition” between Chancellor Angela Merkel’s conservative bloc and the Social Democrats.
Merkel’s party, who lost voters to the far-right want the SPD to agree to a last-ditch alliance with them.