Labour is promising to give unemployed locals "first crack" at jobs by making it harder for businesses to bring in migrant workers.

Leader David Shearer said his party would require proof that employers had "actively engaged" with Work and Income and industry training organisations, before approving workers from overseas.

Immigration NZ would have to assess the impact on wages and working conditions when it considered an application to bring in temporary workers.

"It's estimated that 30,000 workers will be needed for the [Christchurch] rebuild - half are likely to come from overseas," Mr Shearer said in a speech at the Hornby Working Men's Club in Christchurch.

"Migrant labour is an important part of our economy but, given there are 162,000 Kiwis looking for work, we must give them priority."

But Canterbury Earthquake Recovery Minister Gerry Brownlee said Mr Shearer had tried to whip up a jobs crisis in a region where there was massive job growth.

"In January there were 5185 people on an unemployment benefit in Christchurch - today there's 3131," Mr Brownlee said.

The Government had spent an extra $43 million on additional trades training places to help supply skilled workers to the city's recovery. "David Shearer's like a man in a maze with an upside down map and jam jar glasses," Mr Brownlee said.

Mr Shearer said that starting in the construction sector, Labour would impose a "one in a million" condition on companies that won significant government contracts, forcing them to take on one apprentice for every $1m of investment.

He wanted to ensure the Canterbury rebuild was not used as an opportunity to bring in workers prepared to work 12 hours a day, seven days a week for minimum wages simply to undercut competitors.

Government agencies would have to give contracts to local firms wherever possible and undertake a wider economic analysis to ensure maximum benefit to the economy.

Other measures would require employers to train migrant labour "where appropriate" and employers would receive a payment equivalent to the dole if they took on an unemployed person as an apprentice. With 84,000 young people neither in work or education that had to be a priority.

- © Fairfax NZ News