Kevin Rudd and his economy L-Plate

A few weeks back I suggested that Kevin Rudd had Gough Whitlam's understanding of matters economic and Mark Latham's temperament, which is not a good combination. Given those handicaps, he and his campaign team have done an outstanding job of creating a new persona - one that seemingly combines Britain's New Labour revival with the eternal optimism of Ronald Reagan.

As the election looms the government needs to unmask the real Rudd so the electorate can see who it is voting for. In an atmosphere in which the press is doing the government no favours it was always going to be tough for them to get enough air time to let the message sink in.

Fortunately for the government, Kevin Rudd himself has demonstrated how little understanding he really has:

Federal Treasurer Peter Costello says it is clear Kevin Rudd doesn't understand the current income tax system, after the opposition leader slipped up on a question about tax thresholds.

Visiting Queanbeyan on Wednesday, Mr Rudd was asked by a journalist to name the tax rates and where thresholds kick in.

Mr Rudd replied: "Well, as of July 1, if you went through the four thresholds, I think the high threshold kicks in I think at $175,000, then I think it cascades down the spectrum."

Mr Costello seized on the blunder, attacking Mr Rudd in parliament and pressing him to release Labor's tax policy.

"He couldn't name a single rate, he couldn't name a single threshold, and the one threshold that he named of $175,000 ... just doesn't exist," Mr Costello told parliament.

"Since the Labor Party demands an election to be called on a daily basis, you would think they might have the decency of releasing a policy so that people can know what it is."

Mr Costello said tax thresholds don't cascade.

"Cascade is a form of beer, it is not a form of tax threshold.

"This would be amusing if it were not serious."

He said the leader of the opposition did not know what the Australian tax system was.

"He doesn't understand it and he should never be put in charge of people's mortgages, their businesses or their jobs.

"Underneath the glib responses, underneath the media stunts ... there is no economic substance.

"And now he has been exposed as being naked when it comes to understanding the tax system.

"He is a leader of the opposition on trainer wheels."

There's little doubt that Costello is the government's best parliamentary performer. Labor needs to do whatever it needs to in order to not give him any ammunition.