THERESA May's chief of staff expressed his "regret" after he replied to a chain of porn tweets.

Gavin Barwell's account responded to a tweet by "@twinkystar_69" which featured a video of two "teen schoolgirls" and their "mom".

The reply, in which he tagged others users in the chain of messages, was made at 9.21pm on Monday, and was later spotted by social media users.

The tweet was visible for more than a day before being deleted.

A Number 10 source said: “Gavin Barwell replied to this tweet, which was in his timeline, in error.

“He has deleted the reply and regrets the embarrassment this has caused.”

Barwell was MP for Croydon Central until losing his seat in last year's election. He was then appointed Number 10 Chief of Staff by May.

He married his wife in 2001 and they have three sons.