Former Northern Ireland Secretary Julian Smith (Photo: Mark Marlow)

Mr. Smith was the main contributor in talking opposition parties into a return to a power-sharing administration at Stormont in January, three years after it collapsed.

Finance Secretary Sajid Javid resigned the same day, his spokesperson confirmed.

Mr. Johnson appointed Alok Sharma, the former international development secretary, to preside over the UN climate talks to be hosted by the UK this November.