Anyone who has arrived in Australia illegally by boat has been given an October deadline to apply for refugee status, or face deportation.

Immigration Minister Peter Dutton says there are 7,500 people who are yet to prove they are refugees and are owed protection by Australia.

Many arrived without identity documents on boats run by people smugglers up to seven years ago.

Mr Dutton said many are residing in Australia on government funded support, which last year cost around $250 million in income support alone.

He said the new crackdown is firm but fair.

"And the expectation is if people can't make their claim for protection, then they need to depart our country as quickly as possible."