Current practice relies on common law and a 1969 Supreme Court ruling that outlines when abortion is legal.

About 20,000 abortions a year are performed in Victoria.

Mr Brumby said the Bill was not designed to increase that number, simply to remove the threat of criminal proceedings.

All parties have allowed a conscience vote, leaving the parties split.

Mr Baillieu supported the Bill while Mr Ryan, his Coalition deputy, voted against.

Sports Minister James Merlino was among the most outspoken opponents, saying the Bill would mean "open slather" and lead to more terminations. Mr Merlino led the opposition to the Bill, introducing a number of the proposed amendments.

The Bill has caused controversy, with protests inside and outside Parliament, as well as threats to pro-choice politicians. At least one threat has been taken so seriously the police are investigating.

Mr Brumby said on Thursday he was confident the Bill would be passed comfortably, although he conceded the vote would be closer in the Legislative Council.

"We've had a lot of debate," he said.

"At times it's been emotional debate, passionate debate, and we've seen that come through in the Parliament, but it's also been respectful debate."

Mr Hulls, also the Attorney-General, was the most senior Government minister to break ranks with Mr Brumby and vote against the Bill.

As close friends and colleagues since Mr Brumby's days in the Hawke Government, the two discussed the matter before the vote.

The Premier said he respected Mr Hulls's decision.

"I've made really clear in this debate that these are matters that are deeply held, and they are and that's why there is a conscience vote," Mr Brumby said.

"Rob thought long and hard about his position. He spoke to me about that yesterday [Wednesday]. His view, for personal reasons, was that he wished to oppose the legislation. He advised me of that, and I said he should vote as his conscience dictates."

Mr Brumby was asked to expand on Mr Hulls's reasons for opposing the Bill, but declined.

"That's a personal thing for him, and everyone's got their reasons," he said.

An amendment to reduce the limit for an abortion from 24 weeks into a pregnancy to 20 weeks was defeated 48-30.

The debate leading to the Legislative Council's vote on the legislation is due to begin next months. Amendments are expected to be proposed in that chamber as well.

Mr Brumby would not entertain speculation about what amendments might be acceptable to the Government.

He said he expected the legislation to become law by year's end.