Some lawyers have argued a ban could require a change to the German constitution, which protects freedom of religious expression.

The declaration calls for an end to dual citizenship on the grounds that it impedes integration. Under the current law, refugees and those born in Germany to immigrant parents are allowed dual citizenship.

“We reject this divided loyalty,” the declaration reads. “We suggest whoever wants to get involved with the politics of foreign governments leaves Germany.”

It is not clear whether the proposal would apply to nationals from other EU countries, who are also allowed dual citizenship under current laws.

The proposal calls for dual nationals who fight for Islamic State of Iraq and the Levant (Isil) or other extremist organisations to be stripped of their German citizenship.

Under Germany’s federal system, law and order are largely the preserve of the 16 state governments.

The interior ministers who have signed the declaration are all members of the CDU or its Bavarian sister party, the Christian Social Union (CSU), which means there will be considerable pressure for Mrs Merkel’s government to adopt at least some of the measures.

A spokesman for the interior ministry said the declaration was “still under consultation”.