Opposition Leader Tony Abbott has confirmed he will not release the Coalition's full costings until the last week of the election campaign.

The Government has been demanding details from the Coalition about how it is going to pay for its promises.

Mr Abbott says every policy the Coalition releases will be costed, and says Labor has not provided funding details for all of its policies yet either.

However, under questioning on the ABC's 7.30 program, he chose not to provide an exact date for when his figures will be made public.

"We intend to keep putting out policies right up until the last week of the election campaign," he said.

"So when all our policies are out, we will be able to tell you exactly how much we are going to spend, exactly how much we are going to save, and exactly what the overall budget bottom line will be and how much better it will be than under the Labor party."

Mr Abbott said he would not wait until the day before the election before releasing the costings.

He said the Coalition would likely keep the Government's hike on tobacco excise and also its bank levy.

However, he ruled out maintaining Labor's proposed changes to the fringe benefits tax for cars.

"We've said this is a disaster for a motor industry that is under pressure - we are not going ahead with that."

Mr Abbott admitted that a Coalition government would face a "savings challenge" but he again ruled out raising the "overall tax burden".

He also ruled out an increase to the GST.

"The GST can only change if the states and territories agree... and that's the Labor states and the Coalition states, and that's why I say it won't change," he said.

"There will be a comprehensive tax white paper and I don't know what different people will recommend. At the end of the day it will be for the government of the day to [act on]."

Mr Abbott accused Prime Minister Kevin Rudd of hypocrisy over political commercials that painted the Opposition Leader in a negative light.

"Kevin Rudd said at the start of this campaign that at the depths of his heart he wanted it to be positive, but plainly Mr Rudd is not fair dinkum because the attack ads have started," he said.

"People have seen me for almost 20 years in public life. I have published again and again and again, including my book Battlelines. I am prepared to submit myself to the Australian public."

Mr Abbott also dodged a proposal from 7.30 host Leigh Sales to appear on the program to debate Mr Rudd.