Senator Brown called on the Coalition to ''settle down'' into a more constructive role, and tried to reassure its MPs that he had worked with them in the past in a balance of power.

As the Coalition strengthened its opposition to minority government, and a spotlight turned on to Green policies such as a death duty, Senator Brown also spelt out limits to his MPs' ambitions.

Already under the agreement with Prime Minister Julia Gillard, the Greens have given a guarantee not to block supply.

In addition, Senator Brown said yesterday: ''We won't be supporting legislation which raises taxes or puts an impost on the exchequer. That's good practice … If we need to raise revenue through some piece of legislation, then the Greens will be seeking agreement from the government on that before proceeding.''

Senator Brown reiterated that he was open to discussions with Opposition Leader Tony Abbott to make the Parliament work.

''I worked with Prime Minister John Howard. I had the vital vote to enable the last referendum on the republic. I also gave a casting vote there to limit gambling on the internet.''

He said the attack on the three country independents by the National Party was spiteful and old. ''And no wonder the independents have got more out of the government than the Nationals have got in a long, long time.''