Tensions are simmering within the Greens voter base over its handling of tactical and policy questions, with some supporters claiming the party has a tendency to put politics ahead of environmental policy outcomes.

Fuelling the current disquiet was the decision to first renege and then honour a written agreement with the Palmer United Party for an inquiry into the Queensland government's environmental record, among other things.

There are also concerns within the Greens' party room that the decision to bluntly oppose the Abbott government's proposed reintroduction of twice-yearly fuel excise indexation is inconsistent with the Greens' general ethos of lifting cost penalties on fossil fuel consumption.

A Greens source said the fuel tax issue had not been adequately debated, despite a view by some senators that the party should have offered the government a deal to back the indexation – securing $4.1 billion over four years – in exchange for protection of the renewable energy target.