Opposition Leader Tony Abbott is continuing to push out the timetable for when a Coalition government could bring the federal budget back into the black if it wins government on September 7.

This morning Mr Abbott said "we will deliver a surplus as soon as we humanly can" but would not give "an absolute guarantee".

In early August the Coalition committed to return to surplus within a first term, if the budget papers were accurate.

However, earlier today Mr Abbott pushed that out to the first year of a second term, with the same significant caveat.

"If the current projections turn out to be correct, we will do better than Labor, that means we will have a surplus by 2016-17," he told Radio National Breakfast.

The latest economic forecasts, released by the Government in early August, showed Labor delivering a surplus of $4 billion - also in 2016-17.

Yesterday, in his official campaign launch speech Mr Abbott appeared to abandon the first term commitment, instead promising that by 2016-17 the path to a surplus would be clear.

"By the end of a Coalition government's first term, the budget will be on track to a believable surplus," he said at the launch.

Mr Abbott also yesterday laid out a much longer-term surplus ambition, saying "if our vision is realised" that "within a decade the budget surplus will be 1 per cent of GDP".

In early August the Coalition committed to return to surplus within a first term, if the budget papers were accurate.

Treasurer Chris Bowen has pointed to Mr Abbott's changing lines.

"Interestingly this is another change, cause he previously said he'd provide a surplus in 'year one', then it changed to 'sometime over the next four years', then it changed to 'before Labor', now it's apparently 'one per cent in 10 years' time' with no other detail," he said.

But Mr Abbott says the Government's economic statement, released just before the election campaign began, shows the starting point keeps changing.

"We are going to get back to surplus as quickly as we humanly can," he said this morning.

"But we just don't know what the starting point is.

"The last time Labor gave us an update at the beginning of this campaign, they were forced to admit that the budget bottom line had deteriorated to the tune of $3 billion every single week between May and July.

"With that kind of deterioration it would be foolish of me to give an absolute guarantee."

The latest economic forecasts, released by the Government in early August, showed the budget set to be in surplus by $4 billion by 2016-17.

Mr Bowen has again called on Mr Abbott to release his full policy costings.

"He hopes to be prime minister in two weeks time, he wants the keys to the country without showing us the fine print until the last minute," he said.

"And it's simply not on."

Meanwhile Labor is continuing to target Mr Abbott's multi-billion dollar paid parental leave scheme, which it believes is proving to be unpopular in crucial areas such as Western Sydney.

It has seized on comments from Coalition frontbencher, and former leader, Malcolm Turnbull that the scheme is "very generous, there is no doubt about that".

"When people say it's too much or it's too generous that's a reasonable objection," he told Brisbane Radio 4BC.

However, Mr Turnbull defended the scheme as helping women "get the balance right" and said "we believe we can afford it and will afford it".