The quest to pass historic voluntary euthanasia laws has passed a major hurdle after MPs in the Victorian Parliament's upper house voted in favour of a second reading of the bill, paving the way for a final vote within weeks.

A Liberal backbencher kept alive the proposed euthanasia laws, saying he would seek a reduction in the life expectancy time limit from 12 to six months but allow an exception for Motor Neurone Disease.

The vote of Western Victorian MP Simon Ramsay could prove decisive in ushering in an assisted dying regime with a tight final vote expected in the upper house.

The bill, which passed the lower house last month, allows patients to choose to end their lives if they are diagnosed as having 12 months or less to live.

But Mr Ramsay argued that was too long, telling the Parliament he would seek a reduction to six months. But in what could be a crucial concession, Mr Ramsay said he was willing to accept that Motor Neurone Disease could be subject to the original 12-month life expectancy diagnosis.  

"I cannot support a terminal illness diagnosis up to 12 months as part of the criteria," Mr Ramsay said.

Mr Ramsay and his colleague, Liberal upper house President Bruce Atkinson, held the decisive votes on whether the bill passed.

Mr Atkinson, who had kept his view private until today, joined those in favour of the bill.

Its passage would make Victoria the first state in Australia to legalise voluntary euthanasia.

Twenty of 40 upper house MPs said during the debate that they will vote for the legislation, forcing the Andrews government to accept it will have to negotiate amendments to the bill to achieve an outright majority.

Premier Daniel Andrews and Health Minister Jill Hennessy previously said they would not accept amendments.

"It's a raw debate and it challenges our belief systems, our guilt, our motivation where we insist on keeping a loved one alive who wishes to end their suffering," Mr Atkinson said.

"At the end of the day some whose pain cannot be alleviated by palliative care or other means may wish to make a choice to alleviate their pain by passing, passing with dignity."

Mr Atkinson said the debate in parliament had been respectful, but not all messages from the public had taken the same tone.

"Perhaps some of the most intemperate communications to my office came from people who professed to be Christians," he said.

After passing the second reading, the assisted dying bill will be examined in depth in the upper house in the so-called committee stage, before going to a final vote.

However, if amendments are passed in the upper house the amended bill must then go back to the lower house for a final vote.

The committee stage in the upper house could take several sitting weeks.

There was a late impassioned plea against the bill from Liberal Inga Peulich, who spoke of how her mother spent time in a concentration camp during World War II and "treasured every moment of life".

Ms Peulich said she was sickened to think that MPs thought they were doing a public service by encouraging "state-sanctioned death".

"If I faint during the course of this debate please don't be surprised," she said.

The government's leader in the upper house, Gavin Jennings, said proponents of the bill would not allow changes that would jeopardise the integrity of the proposed scheme.

But he left the door open to negotiating on a reduction of the 12-month time frame as long as people who had long-term degenerative conditions were not prevented from participating in the scheme.

Earlier in the day Premier Daniel Andrews said the government was open to boosting palliative care funding in regional Victoria.

"We fully understand that there is more to be done here, we have a budget next year and we are more than happy to look to continue to boost palliative care options," Mr Andrews said.