Britain's divide over Brexit has cost Prime Minister Boris Johnson another member of his embattled government — his own brother.

Jo Johnson has announced he is quitting as an education minister and will step down from Parliament, saying he is "torn between family loyalty and the national interest."

He tweeted that "it's an unresolvable tension & time for others to take on my roles as MP & Minister."

Jo Johnson opposed leaving the European Union during the 2016 referendum campaign and later said the country should not quit the bloc without a divorce deal. But in July he accepted a job in the government formed by his brother, who argued the U.K. must leave the EU on Oct. 31, deal or no deal.