LONDON (AP) — A former U.K. minister says others may step down from the government to protest Prime Minister Theresa May's Brexit plan.

Jo Johnson told BBC radio Saturday it is up to members of Parliament to take a stand.

He said that if others decide to resign, "good on them."

Johnson, the younger brother of Boris Johnson, stepped down as a transport minister Friday and called for a second Brexit referendum. He said May's Brexit plan would damage Britain's national interest.

He said the plan is so different from what had been promised during the 2016 referendum that a second vote is needed.

May has rejected all demands for another vote, saying the 2016 vote in favor of leaving the European Union is definitive.

Difficult negotiations between Britain and the EU continue.