Federal crossbencher Bob Katter has challenged Clive Palmer to a race up the stairs of Parliament after the billionaire suggested the veteran MP was too old to serve his electorate.

Mr Katter, 73, has held the north Queensland seat of Kennedy since 1993 and holds it by a safe margin of 11 per cent.

But in a tweet on Saturday, Mr Palmer, 65, said Mr Katter should close the door on politics ahead of the federal election.

"Bob's done his best, but it's time for him to go and enjoy his retirement," the tweet said.

A promotional video for Mr Palmer's United Australia Party (UAP) also targeted Mr Katter's age and said it was time for change in the electorate.

In the clip, UAP's Kennedy candidate Sue Bertuch said: "[Bob Katter] will be 76 by the end of term — it's time to put Australia first".

Mr Katter laughed off the suggestion.

"I challenge Mr Palmer to a race up the parliamentary stairs, but I have to warn him that I take the stairs two at a time," Mr Katter said.

"We could have a little contest about that, and I think that will decide who is the youngest and fittest.

"One thing I've found in rugby league, when they get older they get cunning and they get very dangerous — I'd like to think I fit into that category."

Mr Katter was first elected as a National Party MP but forged a career as an independent after resigning from the party in 2001.

He founded Katter's Australian Party in 2011.

"As far as intellectual agility goes, in the last three years I have achieved as much as I have achieved in any three years in the rest of my period of existence on the planet," Mr Katter said.

Mr Katter said it was disheartening the minor parties could not do more to work together.

"It is up to us, the leaders of the small parties, to pull together, and I'm deeply disappointed that to date, Mr Palmer hasn't seen it that way," he said.

In the US, the current frontrunner in the race to be the next Democratic presidential nominee is Joe Biden, aged 76.

The ABC contacted Mr Palmer for comment.