The Nationalist Party will decide whether to take action against MP Edwin Vassallo for ignoring the party whip after the final vote on the Marriage Equality Bill on Wednesday, a party spokesman said.

Mr Vassallo broke ranks and voted against the bill on second reading on Wednesday, despite a call for unity by Opposition leader Simon Busuttil.

He was the only MP to vote against, despite several other PN deputies expressing reservations.

WATCH: Watch: Edwin Vassallo to vote against gay marriage Bill

Mr Vassallo said the proposed law was “morally unacceptable” and went beyond the government’s mandate for the introduction of same-sex marriage. He argued that the Bill would pave the way for other laws that would tamper with pro-life legislation.

As expected, his decision, which went against his party’s manifesto proposal for the introduction of gay marriage, fuelled speculation on his future within the PN.

Asked if Mr Vassallo would face disciplinary action, the spokesman insisted that all MPs were expected to toe the party line.

“Mr Vassallo’s vote in defiance of the Whip will be considered once the final vote in third reading is taken next Wednesday,” he said.