Saying yesterday she would vote for any federal disallowance of the ACT laws, the former frontbencher said she would argue against intervention in party-room debates but would remain bound by whatever caucus decided.

Senator Lundy voted in favour of the laws when the previous Howard government successfully disallowed them in June 2006.

The ACT Labor Government is considering reintroducing its civil union legislation which would allow same-sex couples to enter into a formally recognised union with the same rights and obligations as married spouses.

Liberal senator Gary Humphries, who crossed the floor when the Howard government initially overturned ACT legislation on same-sex unions in 2006, said Senator Lundy's professed concern for Canberra's gay and lesbian community was now a sham.

"Her statement is a complete reversal of the position she took in 2006 when the former Coalition government first blocked the ACT's laws," he said.

Senator Lundy said she did not see Rudd Government intervention as a foregone conclusion, holding out hopes for the discussions between federal Attorney-General Robert McClelland and his ACT counterpart, Simon Corbell, which continued inconclusively yesterday.

She noted also that the final form of any ACT legislation, which Mr Corbell has pledged to introduce to Parliament with or without federal agreement before this year's election, was not yet determined.

She acknowledged the prospect of significant personal electoral cost.

"All I could ask the people of the ACT is to understand the position that I'm in and that my role as their representative is to argue the toss within my party to the best of my ability," she said.

She hailed the Commonwealth's "overarching" policy announcement that it would remove discrimination against gay and lesbian couples in about 100 laws, principally involving taxation, superannuation and social-security benefits.

"That's the context in which we ought to move forward on this issue for the ACT," she said. "It's extremely positive ... Let's not spoil it over what is an extremely fine line of disagreement in relation to a ceremony of a civil union, not a marriage."

Senator Lundy's emphasis on the fact that the ACT proposal does not involve "marriage" continued to be lost on Prime Minister Kevin Rudd, who highlighted that no other state or territory was proposing what the ACT had put forward. "... we have got a responsibility to honour what we said to the Australian people before the election. And that is, remove all practical levels of discrimination... on the question of marriage, for us that is sacrosanct, between a man and woman, under the Marriage Act, our position hasn't changed."