Prime Minister John Key says there should be no cause to worry about New Zealanders going to work in the Australian mining boom.

Australia contributed to 40 per cent of the economy and New Zealand wanted a strong Australia.

"We shouldn't get despondent because the mining sector is booming in Australia and sucking a few people into that economy," he said.

He also said that if you were shopping for countries, New Zealand would be a good prospect.

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"If you were really going to go out and buy a country, why wouldn't you want to buy New Zealand?

"Would you really want these other countries that are highly indebted, have hugely inflexible and inefficient systems, don't have the natural resources that we have, don't have the potential that we have."

Mr Key, speaking to the TransTasman Business Circle in Auckland, said Australia was going to spend $450 billion in the mining sector in the next 10 to 12 years and had spent $60 billion in the past decade.

Treasurer Wayne Swan had told him that one of the holes that was being dug in a mining project was so large it could be seen from the moon.

"We have a slightly different approach to mining in this country but that's cool. That is the reality of Australia."

He said protesters against Thursday's Budget needed to be realistic.

"If we don't take a responsible approach and continue to spend money we don't have, the long-term implications are very significant, especially for students."

They were the generation that would have to repay that debt.

New Zealand could not run deficits for ever.

"In the end, if you spend more than you earn it's called Greece - or maybe the Otago Rugby Football Union."

Finance Minister Bill English, speaking to an ANZ post-Budget breakfast in Wellington, said students who had protested against the Budget could get some coverage dragging a few rubbish bins around.

"They need some Greeks to show them how to do it."

The Budget tightened eligibility for student loans and requires higher rates of repayment for student loans.

"This is a pretty moderate containment of Government spend."

A dramatic Budget was Australia's last one which will go from a $44 billion deficit in the current year to a $1.5 billion surplus in the next.

He was not sure New Zealanders would be able to rely on getting a job in Australia any more.

Victoria last week announced about 4000 redundancies in a civil service about the same size as New Zealand's.

That would be the equivalent of New Zealand sacking more than 10 per cent of its public service.