Britain's Secretary of State for Justice David Gauke is seen in a car outside the Houses of Parliament in London, Britain, March 27, 2019. REUTERS/Hannah McKay

LONDON (Reuters) - British Prime Minister Theresa May would have to look closely at pursuing a customs union with the European Union if parliament votes for it, justice minister David Gauke said on Sunday.

Parliament is due to hold a second round of votes on alternative Brexit options on Monday. In a first round, the idea of seeking a customs union with the European Union was one of the most popular options, although it fell just short of a majority.

Asked by BBC TV whether May would have to go back to the EU and negotiate for a customs union if parliament voted for it, Gauke said: “I think she would need to look very closely at that.”

“If parliament is voting overwhelmingly against leaving the European Union without a deal but is voting in favor of a softer Brexit, then I don’t think it is sustainable to say we will ignore parliament’s position and leave without a deal.”

Gauke also said May’s three-times defeated deal was not dead, and was still one of the options open to lawmakers.