He announced this on Twitter.

I resigned as Foreign Office minister this morning. Here is my letter to the Prime Minister. pic.twitter.com/1kpt7rHsF0

- Sir Alan Duncan MP (@AlanDuncanMP) July 22, 2019

“I resigned from my post as deputy foreign minister this morning,” Duncan wrote.

The politician also attached a letter that addressed Prime Minister Theresa May. In it, Duncan said that he contributed to good relations between Britain and Turkey, resumed relations with Argentina and "played a role in difficult relations with Russia."

Earlier, the Minister of Finance of Great Britain Philip Hammond announced his resignation.