Brexit negotiator David Davis on Sunday insisted that Britain would not be forced into accepting unfavourable terms in the face of European Union criticism that not enough progress had been made.

Davis clashed with EU counterpart Michel Barnier this week over the Brexit divorce bill, which the bloc has put at 100 billion euros ($118 billion), a figure Britain rejects.

"What he's (Barnier) concerned about is that he's not getting the answer on money and they've set this up to try and create pressure on us," Davis told BBC's Andrew Marr Show.

"I'm not going to allow them to use that time pressure to force us to do x, y or z."

Barnier demanded on Monday that London start "negotiating seriously" as a March 2019 deadline looms, with talks stalling over what comes first -- the divorce settlement or Britain's future relationship with the bloc.

"I am concerned, time passes quickly," Barnier added.

Davis responded that "the point about the Europeans, they won't talk about the future, they'll only talk about so-called divorce proceedings.

"We are saying, 'you've given us this enormous bill we'll go through line by line', we gave them a two-and-a-half hour presentation, they even complained about that.

"We're going through this very systematically, very British way, very pragmatic way of doing it and of course he's finding it difficult, which is why this stance in the press conference," he added.

The European Union has said there must be "sufficient progress" in three key areas -- EU citizen rights, Northern Ireland's border and the exit bill -- before it will consider post-Brexit arrangements, possibly from October.

Britain believes it is not legally obliged to pay any settlement fee though accepts it will have to pay for any future access to the EU institutions, but is reluctant to name a figure without knowing what that access will be.

Davis dismissed as "silly" EU accusations that no progress had been made.

He also rejected a story in the Sunday Times that said Prime Minister Theresa May would accept £50 billion (54.6 billion euros) as a settlement, calling it "completely wrong".

May is under pressure after her Conservative Party was forced into an informal coalition government due to June's disastrous election result, and faces a parliamentary battle to push through a crucial domestic bill, which would automatically put the EU's laws onto Britain's books when it leaves.

Pro-EU MPs in her party hit out after her de facto deputy Damian Green wrote in the Sunday Telegraph that the party had to support the legislation or risk handing power to Labour and their hard-left leader Jeremy Corbyn.

MP Anna Soubry told the Observer that "any suggestion" that challenging the legislation was "treacherous or supporting Jeremy Corbyn is outrageous.

"It amounts to a trouncing of democracy and people will not accept it," she added