John Key. Photo / Mark Mitchell

John Key. Photo / Mark Mitchell

Finance Minister Michael Cullen has renewed his attack on John Key, saying his gambling currency trader background makes him the wrong man to lead the country in a time of global financial turmoil.

Dr Cullen used the line of attack yesterday, but today ramped it up a notch against the backdrop of Mr Key's former employer Merrill Lynch being bought out in an emergency sale aimed at preventing an imminent collapse.

The fire sale to the Bank of America and the collapse of massive investment bank Lehmann Brothers have sent world sharemarkets tumbling.

Dr Cullen said at a time of global uncertainty Mr Key was the wrong man to run the economy.

"He has got a short-term profit maximising mentality and that is what has brought Merrill Lynch and Lehmann Brothers and these other businesses to their knees.

"Do you want someone like that running the economy when we are going to be going through a difficult period."

He said he believed linking Mr Key back to the massive global company he left eight years ago was legitimate.

"Mr Key has put forward his Merrill Lynch credentials as part an important part of his narrative," he told reporters.

"That doesn't look such a good qualification any longer for running New Zealand's economy."

He said National's planned $50 a week tax cuts would put the Government's books in a poor state to weather the crisis.

Prime Minister Helen Clark also took a shot at Mr Key.

"Mr Key and the National Party are floating a policy of massively increasing New Zealand's borrowing at a time when the money markets are in turmoil.

"This has to be mind boggling stupid. It means they cannot be trusted with the country's economy."

National has said it will not borrow for its tax cuts, but it is yet to unveil what it will cut or repackage to pay for them.

Mr Key today said Dr Cullen's attempts to link him to Merrill Lynch's current problems were absurd and pitiful.

Dr Cullen was "so desperate he was dredging the bottom of the barrel".

He also attacked Labour's economic record, which he said amounted to overtaxing voters so it could put money into its pet projects.