Theresa May’s plans for a post-Brexit trade deal could be blocked by the national and regional parliaments of the 27 member states after a landmark ruling by a senior member of the European Court of Justice.

Eleanor Sharpston, the European Court of Justice’s Advocate General, issued a legal opinion ruling that an EU free trade deal with Singapore must be agreed by all member states.

It means that a post-Brexit deal may have to be agreed by at least 38 national and regional parliaments, including the 27 national parliaments, at least five regional and linguistic parliaments in Belgium and at least five upper chambers.