Boris Johnson has appointed David Frost, his chief Europe adviser, to lead trade negotiations with the EU on his behalf, with no apparent role for Liz Truss, the trade secretary.

Frost will be the direct counterpart of Michel Barnier, the EU’s negotiator for the future relationship, with civil servant deputies from the Foreign Office and Treasury.

He will lead a 40-person task force, reporting into the Johnson’s Downing Street, now that the Department for Exiting the EU (DExEU) is due to shut down on 31 January.

It leaves no role for Truss amid speculation her department could be rolled into the business department as part of expected changes to machinery of government next month.

Steve Barclay, the Brexit secretary, will lose his role on Friday at 11.01pm and the DExEU civil servants are being redeployed.

However, he may be handed back a job in the impending reshuffle, which is linked to changes in Whitehall departments.

There is speculation the FCO may gain control of the Department for International Development, that the Department for Trade could merge into the Department for Business, Energy and Industrial Strategy, and that energy could be made into an independent department again.

There are also rumours that the Department for Digital, Culture, Media and Sport could be wrapped into other departments.