After the resignation of the EU minister Lord Frost, Downing Street said that Liz Truss would take over responsibility for the UK's relationship with the EU.
She will be adding ministerial responsibility to her foreign portfolio with immediate effect.
This means taking over Frost's key positions on all the post-Brexit committees, including the joint committee that oversees the implementation and enforcement of both the withdrawal agreement of 1990 and the trade and co-operation deal that was clinched last December.
Her appointment will be seen as a steady move after Frost's resignation dealt a body blow to an already weakened prime minister, reeling from sleaze scandals and the loss of the byelection in North Shropshire on Friday.
Frost, who had been leading negotiations with the EU, handed in his resignation letter to Boris Johnson last week and had been persuasive to stay on until January until the news was leaked on Sunday.
In his letter of resignation, Frost said it was the introduction of plan B coronaviruses measures, including the implementation of Covid passes, that prompted his decision. He said he had become disillusioned by tax rises and the cost of net zero policies.