British Prime Minister Theresa May says it's inaccurate to suggest Britain is headed for a "hard Brexit" because it does not face a binary choice between curbing immigration and getting a good trade deal with the EU.

When an opposition Labour lawmaker suggested to May in parliament on Monday she had been "talking up" a so-called hard Brexit, in which Britain leaves the EU's lucrative single market in order to impose controls on immigration, she said: "There is no suggestion of that whatsoever."

Asked by another lawmaker about a report in the Sunday Times that the government was considering halving the headline rate of corporation tax if the EU refuses to agree a post-Brexit free trade deal, May told him he "shouldn't believe everything he reads in newspapers".

The questions come as May tried to persuade the leaders of Scotland, Wales and Northern Ireland to work with her government on a common Brexit negotiating position, but the Scottish leader dismissed the meeting as "deeply frustrating".

May says while the devolved governments of the UK's three smaller nations should give their views on what the terms of Brexit should be, they must not undermine the UK's strategy by seeking separate settlements with the EU.

"I don't know what the UK's negotiating position is because they can't tell us," Scotland's First Minister Nicola Sturgeon said after talks at May's Downing Street office.

While England and Wales voted for Brexit in a June referendum, Scotland and Northern Ireland voted to remain, setting the devolved governments in Edinburgh and Belfast on a collision course with London.

At the meeting with Sturgeon and the Welsh and Northern Irish leaders, May proposed setting up a new body to give the three devolved governments a formal avenue to express their views.

In Northern Ireland, there are fears that Brexit could undermine a 1998 peace deal and lead to the reintroduction of unpopular border controls with the Republic of Ireland, an EU member.

Welsh First Minister Carwyn Jones said it was difficult for the devolved administrations to influence the process when there was so much uncertainty over what the government was seeking.