The Federal Government is facing pressure from within its own ranks to begin moves for a referendum on becoming a republic.

A referendum on having an Australian head of state appointed by the Parliament was defeated in 1999.

But the issue has been revived after the Government's 2020 Summit last year called for the constitutional monarchy to be abandoned.

The chair of the Parliament's Legal and Constitutional Affairs Committee, Labor MP Mark Dreyfus, says the Government should hold a plebiscite on the issue soon.

"I think it's possibly already too late to hold a referendum in the first term of the Rudd Labor Government, but it's not too late to move on to a plebiscite to get some kind of preliminary indication of the national will," he said.

"Holding a plebiscite doesn't commit the Government to holding a referendum at any particular time. It is an important preparatory step.

"The other thing we've learnt about the history of constitutional change, or the lack of change to the Australian constitution, is that these things take a very long time. That's a good reason to start now."