Federal Greens deputy leader Adam Bandt says a poll suggesting his party is poised to win two Melbourne seats at this month's Victoria state election should be taken with a grain of salt.

A Lonergan research poll, commissioned by the Greens, shows the party is leading Labor in both Melbourne and Richmond - meaning the party is on the cusp of winning their first lower house seats in Victoria.

"You've got to take any one poll with a grain of salt, especially one that's three weeks out from an election before the big advertising spends have started," said Mr Bandt, who became the first Australian Greens MP to win a seat in the House of Representatives at a federal election.

"But it's good news for the Greens."

The poll comes as Labor leader Daniel Andrews rejected a preference deal offer from the Greens, citing the need to end the instability that has plagued Victorian politics.

Mr Bandt says the Labor party is trying to "out-Liberal the Liberals".

"The Labor party has left the door open to preferencing the Shooters Party, Family First, the religious right, or even the Liberals," Mr Bandt said.