Almost half of Woolworths' support staff have been made redundant at the troubled retailer's head office in London and in Castleton, near Rochdale, where its HR administration department is based.
Administrators Deloitte said 450 of the retailer's 1,100 support staff have lost their jobs. It confirmed, however, that there are no job losses in its distribution centres or high street stores.
Neville Kahn, joint administrator and reorganisation services partner at Deloitte, said: "The stores and distribution centres will continue to trade as normal, but with a simplified core structure supporting them.
"The administrators, supported by management, are still actively seeking a purchaser for the business as a going concern, with discussions being held with a number of interested parties. We are working hard to ensure that any sale of the business, in whole or in part, will preserve jobs.
The news comes as the Woolworths annouced its "biggest ever sale", in which extra staff have been hired to cope with demand.
Deloitte said there had been no redundancies at Woolworths' wholesale distribution business Entertainment UK, which was also placed in administration last week.
Jobcentre Plus staff will visit both sites to provide support and advice to employees who have been made redundant, and the Insolvency Service's Redundancy Payments Service has put together a special team to quickly approve claims for employee entitlements.