Key Points:

National Party leader John Key is pledging to give senior public servants more involvement in Cabinet processes if he leads the next government, as he delivers a double-edged message to the Wellington bureaucracy.

Mr Key ventured into potentially hostile territory yesterday to make a speech to the Public Service Association, the union that represents more than 55,000 people working in government departments and state-funded agencies.

National promises to cap the number of bureaucrats and to redirect resources towards frontline staff. These ideas have not been welcomed by many in the public service.

But Mr Key managed to get through his speech without incident partly because he carefully mixed positive messages for the public service in among the harder-edged policy he acknowledged union representatives wouldn't like.

"National will expect a high degree of professionalism from the public service, part of which is telling ministers what they are not comfortable hearing," Mr Key said. "As part of this openness, policy advisers will be able to take part in Cabinet committee discussions where it is appropriate.

"That's because advisers can exercise better judgment if they have a better understanding of the context in which they are making those judgments."

Under the previous National government, senior officials sat in on Cabinet committee meetings, but this changed when Labour took power and the officials were made to wait outside, called in only when they were needed.

Mr Key later said National believed there was now a "disconnect" between what the Cabinet talked about and what came out of the state sector.

"I think that's producing a lot of reports which ultimately get wasted because they're not relevant to the ministers," he said.

"What we're saying is that we want to make sure that the Cabinet committees are operating with the best information available and that the work that's being undertaken by the government agencies on our behalf is absolutely in tune with the thinking."

Mr Key peppered his speech with pledges that an incoming National government would not be concerned about whether people in the public service had links to other political parties.

But he couldn't avoid the fact that National's attacks in recent years on the growth of the bureaucracy have not gone down well with many who were in the audience.

He argued National's tax cuts would not come at the expense of public services - which some in the audience clearly did not agree with.

And Mr Key said while the PSA had been critical of his policy to stop the growth of the "core bureaucracy", he had responsibilities that were wider than those of the union.

"You have responsibilities to your members, which I recognise," he said.

"But if I become prime minister I will have responsibilities as well - to the people of New Zealand. I need to be able to look them in the eye and assure them that the money they pay in tax is being spent wisely."

Progressive MP and senior Cabinet Minister Jim Anderton later attacked Mr Key's speech. He said it was simply not credible that National could promise billions more dollars worth of tax cuts and not affect public services.

"He won't say tax cuts are better than a particular service such as healthcare for all," Mr Anderton said. "Instead he pretends you can have everything."