London (CNN Business) Celebrity chef Jamie Oliver's restaurant empire in the United Kingdom has collapsed.

The entrepreneur and anti-junk food campaigner said Tuesday that the restaurant business was being placed into administration, or bankruptcy protection.

The group includes Jamie's Italian chain, Jamie Oliver's Diner at Gatwick Airport as well as steakhouse Barbecoa and Fifteen London, a restaurant Oliver started in 2002 to train young unemployed people.

KPMG, which has been appointed administrator, said in a statement that 22 of the group's 25 restaurants have closed, with the loss of about 1,000 jobs.

"Both Jamie's Italian restaurants and Jamie Oliver's Diner at Gatwick Airport will continue to trade in the short term while the joint administrators explore options for the site," KPMG added.

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