Michel Barnier has attacked key parts of Theresa May's Brexit plans and suggested that splits in the Conservative Party could force her to go back to the drawing board.

Responding to the Government’s Brexit white paper for the first time, the EU’s chief Brexit negotiator challenged the Prime Minister’s ‘third way’ customs arrangement and proposals for a common rule book which would see the UK maintain regulatory alignment on agri-foods and industrial goods.

Mr Barnier dissected the UK’s proposals piece-by-piece, raising concerns about goods and services, tariffs, and the ongoing uncertainty over the Irish border.

He also claimed that splits within Mrs May’s Government meant that the UK’s negotiating position may not be set in stone, adding that the “debate is not over yet”.

It came after Mrs May gave her own Brexit speech in Belfast on Friday morning, in which she warned her Eurosceptic backbenchers that they cannot “wash their hands” of Northern Ireland and the border issue in their pursuit of a hard Brexit.