Prime Minister Julia Gillard has attacked Opposition Leader Tony Abbott for "breaking his word" as the two failed to break the impasse over changes to the speaker's role.

Labor and the Coalition are bickering over whether the proposed changes to the position of speaker - agreed to earlier this month in a deal with the independents - are in breach of the constitution.

Fronting the media this afternoon, Ms Gillard said she had a phone conversation with Mr Abbott during which they spoke about changes to the speaker role.

She said Mr Abbott would not agree to the new rules for the speaker's position, which centre on arrangements for voting.

And Ms Gillard accused Mr Abbott of breaking his word.

"I view this to be an extraordinary set of events," she said.

"We gave our word. Our intention has always been to honour our word. I would have thought it was a reasonable expectation that the Leader of the Opposition would also honour his word.

"He has now said to me, and effectively to the Australian people, that his word is worth absolutely nothing."

Ms Gillard refused to say if she would now keep Harry Jenkins in the role and would not speculate on whether she would try and woo a Liberal or National MP to take up the position.

Numbers will be crucial in the new Parliament with the Government holding just a two-seat majority over the Opposition.

During the election deadlock, Mr Abbott agreed to the reform deal but began to back away from it after independent MP Rob Oakeshott put his hand up for the speaker's job.

The changes would see a member from the opposite side being paired with the speaker, who does not have a deliberative vote, during divisions.

This would mean the loss of the speaker's vote would effectively be neutralised in Parliament.

The Opposition argues the changes are in breach of the constitution and wants Mr Jenkins to remain in the chair.

But Ms Gillard says the changes, which would need to be verbally agreed to between the two sides, would have been workable.

"Mr Abbott says he doesn't believe that these questions can be dealt with as a matter of honour or a gentlemen's agreement. I of course disagree with that," she said.

Mr Abbott says the Opposition has carefully looked at advice from the Solicitor-General on the matter, but rejects any notion that it is not a constitutional breach.

"It's clear from a close reading of the Solicitor-General's opinion that the only basis from which the speaker can be paired is an informal arrangement," he said.

"Legislation that passes the Parliament is too important to be based on an informal arrangement."

Mr Abbott says he still backs the rest of the reform deal.

"I support parliamentary reform. I continue to adhere to every aspect of the agreement, except the pairing arrangement, which we now know is fundamentally unsound and just simply cannot proceed," he said.