THIS is one boomerang, reckons Merv Ryan, that ought to come back.

The 54-year-old spokesman for the Gwaegal people of southern Botany Bay has joined forces with the local federal MP, Scott Morrison, to call on the British Government to buy and return a boomerang owned by Captain James Cook, as a gesture of reconciliation.

The 56-centimetre boomerang, along with two clubs thought to have been collected by Cook during his 1770 voyage, is up for auction at Christies in London on September 25 with an estimate of $192,000.

In 1770, Mr Ryan's ancestors greeted Cook at Kurnell "with long pikes and a wooden weapon made something like a short scymetar", according to the diary of Cook's botanist, Sir Joseph Banks.

The outcome of that encounter is now history - they were shot at, Banks wrote - but Ryan says it is never too late to make amends.

"It would be a good thing for Britain to turn around and say we will do this because of what we did to the Aboriginal people in the beginning - as a goodwill gesture."

Mr Morrison will today ask the Heritage Minister, Peter Garrett, the Foreign Minister, Stephen Smith, and the Prime Minister, Kevin Rudd, to request that Britain buy the boomerang and return it. If they refuse, Australia should buy it, he said.

"These things only come up from time to time … we're talking about the first meeting between indigenous and modern Australians, so it's in a category of its own."

With the 250th anniversary of Cook's landing approaching in 2020, Morrison and Ryan hope the boomerang will be the centrepiece of a new museum at Kurnell.