Joe Johnson, the younger brother of British Prime Minister Boris Johnson, said he would resign as minister and deputy after he felt "torn between his loyalty to his family and the national interest."

"I was honored to represent the Orbington Circle in the south east of England for nine years and served as minister under three prime ministers," Joe Johnson, 47, wrote in a tweet on Twitter.

He added: «In recent weeks I have been torn between my loyalty to my family and the national interest, it is an irresolvable tension and it is time for others to assume my role as a member of parliament and minister».

Joe Johnson supported his brother's government by voting against a bill this week to avoid a Brexit without an agreement, as well as his call for early elections.

Their sister Rachel wrote on Twitter today that the family «avoid raising the issue of the exit of the country from the European Union, especially during meals, where we do not want to unite against the Prime Minister!».

Downing Street's government headquarters announced that Boris Johnson thanked his brother for his service "and that the prime minister as a politician and brother understands that this was not easy for Joe."

Labor MP Ian Murray said Joe Johnson's resignation was "devastating."

"Even Boris Johnson's brother knows that he could not be trusted to make decisions for the national good," Murray wrote on Twitter.

Joe Johnson was a participant in the campaign to stay in the European Union in the exit referendum in 2016 and supported calls for a second referendum.