Prime Minister Kevin Rudd has brushed aside criticism for using notes in , saying he acted in "good faith" and joking that "there's a limit to how much you can scribble down on the palm of your hand".

The debate rules, agreed to by both parties and the board of the National Press Club, stated that the "leaders may have a pen and paper on the lectern, and no other documentation or props".

The Prime Minister said he likes to use notes so he can be "as accurate as I can".

"If someone had have said to me it was not proper to take notes along to a debate then sure, that's fine," Mr Rudd said.

"I was in receipt of no such advice.

"It'd be rather odd if you went to a platform, watched by several millions of people, thinking that you could do something on the sly. You can't.

"So I acted in good faith. I think everyone would accept that."

Mr Rudd said he used notes when he debated John Howard in 2007 and joked that he needed them last night to remember all of the Opposition Leader's "three-word slogans".

Tony Abbott has let others lead the attack on Mr Rudd over the breach.

"I don't blame anyone for having to use notes. Sometimes I have to use notes myself," he said at a campaign event in the Melbourne based seat of Deakin.

"The problem with the Prime Minister last night was not that he was reading from notes, it was more that the notes weren't worth reading, that was the problem last night."

At the same event, Liberal Senator Helen Kroger described Mr Rudd's notes as "cheat sheets".

Last night's debate was the first - and perhaps final - face-to-face exchange between the two leaders.

Although both are pushing for more encounters, there is so far no agreement on where or when they might occur.

The debate focussed heavily on the economy, though the Prime Minister did promise to move towards legalising same-sex marriage in the first 100 days of a re-elected Labor government.

Mr Abbott promised to make a decision about the location of Sydney's second airport within the first term of a Coalition government.

On that issue, Mr Rudd failed to repeat his Deputy's promise made last month to start building the second airport within the next term if Labor is re-elected - though he has mentioned it this morning.

Otherwise, the debate failed to elicit much new information about what each leader would do if they won.

They both opened with lines from their stump speeches, Mr Rudd promising Australians "a new way" and Mr Abbott offering to "restore hope, reward and opportunity".

And both reprised old lines of attack on the other, with the Opposition Leader citing "pink batts that caught fire in people's roof" and the Prime Minister pointing to his opponent's previous comments on climate change saying "we've never doubted the science - unlike some".

The economic debate is likely to intensify tomorrow with the release of the latest budget figures from Treasury and Finance in the Pre-election Economic and Fiscal Outlook.