Britain's Prime Minister Theresa May speaks at the Royal Free Hospital, London June 18, 2018. Stefan Rousseau/Pool via Reuters/File Photo

LONDON (Reuters) - Britain must be free to protect its leading position in the services sector, including finance, after it leaves the European Union, Prime Minister Theresa May said on Monday.

Foreign Secretary Boris Johnson quit on Monday over May’s plan for Brexit, which includes a free-trade area for goods but little detail on the approach to services.

“We believe it is important to maintain more flexibility in how we’re dealing with services,” May told parliament.

“On services, we want to be free to ensure that we are able to put in place what we believe is necessary to maintain our key position in services, not least on the financial services.”

May told parliament in a heated session that her plan was “not a betrayal” of the referendum vote.