Key Points:

Labour yesterday accused National Party leader John Key of pork barrel politics and said the cost of roading projects he had announced was based on inaccurate figures.

National rejected the criticism and said all the costings were accurate and based on the Government's own 10-year plan.

Mr Key went to Tauranga yesterday to promise National would turn Tauranga's road corridor into a $100 million four-lane state highway within six years.

"The Tauranga central corridor is currently not planned or funded," he said.

"National is promising to meet the project's full cost of $100 million to resolve this emerging Achilles heel of Tauranga's roading network."

Earlier in the campaign he said National would fast-track the remaining parts of the Waikato Expressway linking Hamilton and Auckland at a cost of $790 million over 10 years.

Transport Minister Annette King said the investigation and design phases of the Tauranga central corridor had not been completed, so there was no accurate costing for the project.

"Yet Mr 'Pork Barrel' Key is telling the independent New Zealand Transport Agency what it has to do," she said.

"The investigation and design phases don't include a tunnel. Mr Key has decided to put one in. A tunnel option hasn't even been scoped, let alone costed."

Ms King said that when Mr Key said the Waikato Expressway would be completed for $790 million he had forgotten to add the cost of three bypasses.

"The extra funds actually needed to complete the expressway will certainly be more than a billion dollars, not $790 million, and may be even more than $1.4 billion," she said.

A spokesman for Mr Key said the cost of the bypasses had been taken into account and was in the Government's 10-year plan which National was going to implement.

The spokesman said Mr Key had not specifically mentioned the bypasses because it was known they were in the plan.

New Zealand First's transport spokesman, Peter Brown, said the Tauranga roading announcement was a vote-buying move to head off the threat posed by Winston Peters, who is standing in the electorate.