Tesco is shutting its head office as well as 43 unprofitable UK stores as part of a raft of new measures as new boss Dave Lewis battles to turn around the group's fortunes.
Britain's biggest supermarket made the announcement as it revealed like-for-like sales for the 19 weeks to January 3 fell by 2.9%, though they were not as bad over the six-week period, with a fall of 0.3%.
Tesco also said it was to close its final salary pension scheme and shut its main headquarters in Cheshunt, Hertfordshire, in 2016, moving to Welwyn Garden City.
A restructuring of central overheads is expected to save £250m a year.
In addition to the shutting of shops, the group announced a "significant revision" to its store-building programme.
It is also selling Tesco Broadband and UK download business Blinkbox to TalkTalk and exploring options for the disposal of its dunhumby data business, as well as cancelling a final-year dividend for 2014/15.
The raft of announcements came as the supermarket also fired the latest salvo in a New Year price war, by cutting the cost of some of its best-known products.
Chief executive Dave Lewis said: "We have some very difficult changes to make. I am very conscious that the consequences of these changes are significant for all stakeholders in our business but we are facing the reality of the situation.
"Our recent performance gives us confidence that when we pull together and put the customer first we can deliver the right results."
Pauline Foulkes and Joanne McGowan, national officers of the Usdaw union, said: "We note the difficulties faced by Tesco and we are just as keen to ensure that the company is able to turn the business around and improve its performance.
"We recognise that some change is inevitable, given the challenges faced by the business but we will want to ensure a fair and balanced approach is taken.
"On that basis, we have arranged meetings with the company to understand the rationale behind these proposals and begin discussions at the earliest opportunity.
"We recognise that this is a worrying and difficult time for our members and reps, who will have lots of questions.
"However, the announcement has only just been made and as we go through the consultation process in the coming days and weeks, the situation will become clearer and we will be better placed to answer their questions.
"We want to reassure our Tesco members that Usdaw is committed to supporting and protecting them throughout this process and will continue to communicate and update them as discussions progress."