One of Australia's foremost budget experts says hundreds of billions of dollars in spending will be added to the nation's books if key budget measures do not pass through the Senate.

Chris Richardson, from Deloitte Access Economics, has told ABC TV's 7.30 program the Senate plan to block cuts and new fees from the Abbott Government's first budget will cost $300 billion over the next decade.

"Essentially, the Senate is not just blocking the budget for the next handful of years, but blocking the budget for the next decade," he told 7.30.

"And it says deficits as far as the eye can see unless there is some breakthrough in political processes.

"Across the next 10 years, and when you add in the interest bill as well, you're talking about $300 billion that the Senate is implying it will impose."

Mr Richardson says the budget situation has "gone backwards" already.

"The budget is in a lot of trouble," he said.

"What's happening in the Senate right now is bigger than people realise. The budget was big news with the savings it was making.

"In fact, the Senate looks like it's blocking enough things that the savings the Government was going to make across the four years, they've completely disappeared, and more."

In its May 13 budget, the Government announced billions of dollars in cuts, including to family tax benefits, health and education, and a $7 fee on GP visits.

Many of the measures are facing defeat in the Senate, with Labor, the Greens and the Palmer United Party saying they will oppose them.

One of the most significant budget measures was the reinstatement of a biannual increase to the fuel excise, which would have added $2.2 billion over four years to the Government's coffers.

But that measure has been killed off by the withdrawal of any support from the Greens, who judged it was pointless to negotiate with the Government.

Mr Richardson says that decision "surprised" him.

"I'm not clear you'd be calling them the Greens at the moment," he said.

"They sound a bit more like the Australian Motorists Party in terms of their response."

Hockey warns of more cuts if budget negotiation fails

Earlier on Wednesday, Treasurer Joe Hockey warned he is prepared to bypass Parliament and force through new spending cuts if Labor and the Greens do not come to the table on budget saving measures.

"I say to the Labor Party and to the Greens - if your instinct is to say 'no' immediately and to stick with that, you are dealing yourself out of having influence on public policy," he told ABC radio's AM program.

"Because if the immediate reaction is 'no', with no opportunity [for] open discussions in relation to matters, then there are other alternatives that we can take.

"We are open to discussions - as any reasonable Government would be - but we are not going to step away from the fact that the budget needs to be repaired."

Labor says it is willing to negotiate with the Government, but points out that the Treasurer and Finance Minister have both previously ruled out making changes.

"Today he's talking about alternatives, [but] we've been told there's no alternatives," shadow treasurer Chris Bowen told Radio National.

"So if the Treasurer wants to put up alternatives, let's get rid of the bluff and bluster and the beating of the chest with which he specialises, and get down and tell us what the alternatives are."