The ACT Government says a move by Tasmania to give greater rights to gay couples shows Canberrans are being treated unfairly by the Commonwealth.
The Tasmanian Government will allow same-sex couples to register their relationships from the date a ceremony is held.
Gay couples in the ACT can register their relationship but cannot hold a legal ceremony.
Attorney-General Simon Corbell says it is a significant move and the ACT should have the same right.
"What this highlights is that the Federal Government has been discriminating against the Territory on this matter," he said.
"The Territory has proposed a particular course of action, it was rejected.
"Now of course the Tasmania Government has done it and they don't have the same options to bully the Tasmanian Government into submission."
The ACT Government had tried to introduce legal ceremonies as part of its 2008 Civil Partnerships Act but the Federal Government intervened saying the arrangement was too similar to marriage.
An ACT Greens bill currently before the Legislative Assembly aims to change that.
Mr Corbell says the Government will try to amend the bill to give gay Canberra couples the same rights as those living in Tasmania.
"As a minimum we will be moving to amend the bill that's currently before the Assembly to allow for the same provisions that have been announced by the Tasmanian Government, that will allow registration of civil partnerships to be back-dated to the date of any private ceremony that may have taken place," he said.