FILE PHOTO: British and EU flags flutter outside the Houses of Parliament during a pro-Brexit and anti-Brexit demonstration, ahead of a vote on Prime Minister Theresa May's Brexit deal, in London, Britain, January 15, 2019. REUTERS/Eddie Keogh

LONDON (Reuters) - Britain is still seeking legally-binding changes to the Brexit deal it has negotiated with the European Union, Prime Minister Theresa May’s spokesman said on Monday, adding that talks were at a critical stage.

The spokesman said progress had been made in the discussions but that more work was still to be done. Brexit Secretary Stephen Barclay and Attorney General Geoffrey Cox will travel to Brussels for further talks on Tuesday.