A Liberal party room meeting will decide whether to back the bill, which would give same-sex couples the same rights as married couples in such areas as medical treatment, superannuation and property transfers.

A senior Liberal source said that following the amendments, the party room was likely to reverse its opposition and support the bill.

It is expected that the Liberals will move their own amendments to the bill rather than block it outright, with their biggest remaining concerns focusing on wills and probate.

The bill - to be debated in parliament today - must have the support of the Liberals, who control the upper house, if it is to become law.

Cabinet has approved two amendments to allay concerns that the bill undermined families and long-term relationships.

Attorney-General Rob Hulls said the changes would put into law the requirement that a domestic partnership existed only where there was a loving and caring relationship.

"It makes it crystal clear that this legislation applies to bona-fide domestic relationships where there is a loving and caring relationship regardless of the sex of the couple," he said.

"The Liberal Party has no choice but to support this bill if they want to end discrimination against gays and lesbians in Victoria."

The government introduced the Statute Law Amendment (Relationships) Bill last year, but it stalled after Mr Hulls fell ill in March and Liberals said it was badly worded.

The recent changes were welcomed by Gippsland West MP Susan Davies, whose vote would ensure its passage through the lower house.

But fellow independents Russell Savage and Craig Ingram indicated the amendments were insufficient to win their support.

In a hopeful sign for the government, Opposition Leader Denis Napthine said the changes "seem to be heading in the right direction". The bill was discussed by the shadow cabinet yesterday.

Dr Napthine said the original bill was poorly drafted, with serious consequences for families, children and long-term relationships. He said university students sharing a house would have been considered to be in a domestic relationship.

Dr Napthine said the government's changes were substantial.

A senior Liberal source said that "now the momentum is with the bill, not against it. Virtually every objection that was made has been dealt with, either by amendment or agreement."

Debate is expected to be lively in the party room meeting, with some MPs seen as opposed to the bill under any circumstances.