The Greens have offered the Abbott government its first chance to pass its Direct Action climate policy, but only if it agrees to toughen the scheme and preserve Australia's renewable energy target.

In a speech to the National Press Club on Thursday, Greens leader Christine Milne said her party was prepared to negotiate to put some "spine and rigour" into the government's replacement for Labor's carbon price, despite also describing Direct Action as a "pathetic, ill-defined excuse for climate action" in its current form.

Direct Action offer: Greens Leader Senator Christine Milne at the National Press Club in Canberra. Credit:Andrew Meares

In the first sign the government could yet pass laws it needs to enact Direct Action, the centrepiece of which is a $2.55 billion emissions reduction fund, Senator Milne said the Greens could support the idea with some changes and a commitment to keep the renewable energy target as part of the policy.

The Greens, Labor and Palmer United Party have so far indicated that they will oppose Direct Action, which could potentially lead to the emissions reduction policy being blocked in the Senate.