JAMIE Oliver's business woes have deepened with his Australian restaurant group falling into voluntary administration.

The celebrity chef's UK restaurants have been in financial strife amid rising costs and consumer caution, partly as a result of the Brexit vote, and his Canberra venue has now been closed.

The Jamie Oliver Restaurant Group Australia, which operated six Jamie's Italian restaurants in Australia, slipped into voluntary administration on Monday.

The Canberra restaurant was closed down, while Brisbane-based Hallmark Group will take over the management of Jamie's Italian restaurants in Sydney, Brisbane, Perth, Parramatta and Adelaide.

A statement by his restaurant group said Australia was still one of his best performing international markets.

"We'll be working closely with Jamie and the UK team, staff and local suppliers to keep driving the business forward and delivering exceptional experiences across the country," a statement by Hallmark said.

Hallmark, the owner of Brisbane Irish bar Finn McCools, said it was also looking at new suitable locations to expand the Jamie's Italian chain.

Mr Oliver, the face of Woolworths' advertising campaigns and who is credited with helping turn around British supermarket chain Sainsbury's, bought the Australian Jamie's Italian restaurants from receivers of the failed Keystone Group in March 2017.

In January, 12 of his UK restaurants closed despite Mr Oliver having reportedly pumped his own money into the business to keep it going.