Vincent and Martine Lenoir, from the French-speaking Wallonia region of Belgium, spoke to CNN about their difficulties in securing French citizenship despite being fluent in the language.

“I am the commercial director of a French company, my wife wrote a book in French,” Mr Lenoir said.

However, French authorities have refused to accept the couple’s degrees from French-speaking universities in Belgium as evidence of their ability to speak French to at least a B1 level.

A spokesperson for the government office in the southern French department of Drôme said the documents did not meet requirements set out in French law.

The Belgian naturalisation process, by contrast, accepts a degree from a university in France as evidence of French language ability.

Mr and Mrs Lenoir say they will now have to restart the French naturalisation process as a result of their unexpected rejection.