The belief is so deeply ingrained in this country that we instinctively doubt an ' />

Corruption is foreign to New Zealand's government, we believe.

The belief is so deeply ingrained in this country that we instinctively doubt an accusation such as that levelled against the Government this week over the ministerial vehicle fleet replacement.

The Labour Party revealed that the National Party received a $50,000 donation from an Auckland BMW dealer two days after a meeting between the Prime Minister's chief of staff and the Department of Internal Affairs which approved the purchase of 34 new BMWs.

A month earlier the dealer, Team McMillan, had held a function attended by the Prime Minister.

Both John Key and the company's managing director, Bob McMillan, have denied the function and the donation had any connection with the fleet purchase.

Mr Key accused Labour of a "baseless smear on my integrity". Mr McMillan said, "We have no involvement whatsoever. It is handled by BMW New Zealand. We are a privately owned family operation. I haven't supplied a single vehicle to any Government in my life."

His only interest in the Government's BMWs, he said, was a possible bid to buy the old ones, but he had not expressed that interest to Mr Key or the Internal Affairs Department.

That seems to be that; even Labour does not appear to believe there was anything more to the meetings or the donation. "I'm not suggesting the Prime Minister's office is corrupt," said front-bencher Trevor Mallard, "but there is a perception of conflict of interest."

In any other country there would be that perception, but here? We are blessedly confident in the probity of our public service. The country rates close to zero on international measures of corruption and local industry representatives who deal abroad say we do not realise how lucky we are.

The public can be reasonably confident the ministerial limousine replacement was conducted at arm's length from the Cabinet because the Opposition has raised it before and Mr Key appeared genuinely angry that he had not known about a department-level decision that had the potential to embarrass him with its costs and comforts.

It also turned out to be a decision made in line with a contract entered into under the previous Government.

Labour has made many attempts of late to mine the Prime Minister's Department for supposed profligate spending. Most of what it has turned up has been no more telling than a BMW's heated seat, but this week the Opposition did its work.

Even if appearances deceive, the meetings and the donation deserved to be probed.

Political leaders would do well to ensure their benefactors have no association with a brand the Government is purchasing. The incident also underlines the correctness of divorcing party donations from purchasing decisions.

No country can be too vigilant against corruption. If this is one of the world's least corrupt places, it is at risk of assuming too much. Corruption, after all, is not completely unknown here.

A former MP, Taito Phillip Field, went to jail for work done for him in return for immigration help.

An immigration official, Mary Anne Thompson, resigned in 2008 over indiscretions that included helping relatives enter New Zealand.

Exceptions are sufficiently rare to prove the rule: we retain a culture of honesty in public life that we ought never to take for granted.