The Northern Ireland Secretary is believed to have resigned this morning.
James Brokenshire is thought to have stood down due to ill health.
Theresa May is expected to announced a Government reshuffle today.
A source close to the 50-year-old minister said he had decided to stand down because he was facing major surgery within the next couple of weeks.
The Old Bexley and Sidcup MP is a close ally of Mrs May, having served under her for five years at the Home Office, and he was not among ministers who were predicted to go in the Prime Minister’s first major reshuffle since she took office.
Explaining his decision, a source close to Mr Brokenshire said: “He has a small lesion on his right lung and is getting major surgery in the next couple of weeks.”