The federal government now has a clearer idea of what budget measures Labor and the Greens will oppose and support.

Billions of dollars in federal budget savings are at risk after Labor and the Greens finalised which Abbott government cuts they will oppose and support.

But Opposition Leader Bill Shorten won’t yet say how Labor would fill the savings gap beyond scrapping the $22 billion paid parental leave scheme.

The Labor caucus on Tuesday agreed to block a raft of budget measures aimed at cutting $15 billion in spending on pensioner benefits and concessions as well as family payments.

“Tony Abbott has a fight on his hands with this rotten, unfair budget,” Mr Shorten said.

The Greens also created a $2.2 billion hole in the budget by overruling leader Christine Milne and agreeing to oppose the re-indexation of fuel excise to inflation.

Senator Milne initially had said the Greens would support bringing back indexation if the money raised could go towards public transport, but now opposes it outright as a “tax on families”.

Prime Minister Tony Abbott told parliament Australians recognised the nation could no longer live beyond its means.

He is confident they generally appreciate the government had to take some tough decisions.

“Some of those tough decisions involve saying no more cash splashes with borrowed money,” Mr Abbott said.

Labor deputy leader Tanya Plibersek said Mr Abbott planned his own “cash splash” – a $22 billion parental leave scheme.

Palmer United Party leader Clive Palmer, whose three senators will play a key role from July 1 in passing bills, also urged the government to drop its parental leave scheme.

He is advocating cutting $36 billion from the national broadband network, scrapping the $2.5 billion Direct Action climate plan and saving $20 billion from reworking the Navy’s submarine program.

Mr Abbott said he appreciated that Mr Palmer was coming up with alternative savings.

“(They’re) not very good ideas, but some ideas – unlike the leader of the opposition who is all complaint and no solution.”

Mr Palmer will unveil how his party will approach the carbon tax repeal on Wednesday.

Labor has agreed with a number of budget measures, including reducing the Family Tax Benefit B primary earner income limit from $150,000 a year to $100,000 and including untaxed superannuation income in the assessment for seniors health card.

The two budget bills are expected to pass through the lower house this week, setting them up for debate in the Senate in a fortnight.

The caucus decision came as a new Essential poll showed 72 per cent of voters believed Mr Abbott had broken election promises, including 49 per cent of coalition voters.

Meanwhile, Mr Shorten held a minor reshuffle of his frontbench in the wake of the retirement of six senators.

David Feeney adds veterans affairs to his role as shadow minister for justice, while Joel Fitzgibbon adds rural affairs to the agriculture portfolio.

Amanda Rishworth is elevated to the shadow ministry in the assistant education portfolio.

Senator Lisa Singh (environment) and lower house members Graham Perrett (attorney-general) and Nick Champion (health) become shadow parliamentary secretaries.