"The growing politicisation of the German debate on arms exports ... is jeopardising European defence cooperation," wrote the envoy, Anne-Marie Descotes.

"The unpredictability of German policy on export controls ... is causing concern among Germany's European partners," she wrote in an opinion piece for Germany's Federal Academy for Security Policy.

Descotes' comments came as Chancellor Angela Merkel's cabinet is considering whether to extend an arms sales freeze on Saudi Arabia that has impacted other European exports.

Berlin imposed the moratorium on countries involved in the Yemen war in October following the murder of Saudi dissident journalist Jamal Khashoggi in Istanbul.

The move angered both Paris and London because of its knock-on effect on common European defence exports, and French President Emmanuel Macron labelled "pure demagoguery" Berlin's call for other countries to follow suit.

Descotes charged that such decisions "reinforce the impression that the German export control system is not restrictive, but unpredictable".

Often the use of even small German components such as seals or ball bearings was leading to lengthy delays for manufacturers elsewhere, as well as to penalty payments and lost contracts, she wrote.

Some defence companies are already building products marketed "German free" in terms of components.

Descotes argued that "this problem goes far beyond the countries involved in the Yemen war and also affects exports to Senegal, India, Indonesia or Niger".

Germany and France are among the world's top arms exporters, a club that is led by the United States and also includes Russia, China and Britain.

Descotes argued that Germany's stance could impact large future projects, among them ambitious Franco-German plans to jointly develop the so-called Future Combat Air System of fighter jets and drones by 2040.

Human Rights Watch this week argued Germany should maintain the embargo and other countries "should follow suit".

The New York-based group pointed to "the terrible toll on Yemen's civilian population and serious laws-of-war violations" in the conflict which the United Nations calls the world's largest humanitarian catastrophe.