B&Q is cutting about 400 office-based jobs in response to a slowdown in consumer spending that is hitting the home improvement sector hard.
Consumer appetite for DIY is cooling
At its head office in Hampshire, 220 jobs are to go and a further 80 regional posts will be scrapped, while 100 vacant posts will not be filled.
The restructuring, which will not see any job cuts at B&Q's 339 stores, could involve compulsory redundancies.
The cuts come after an operational review by chief executive Ian Cheshire.
B&Q's announcement comes as a downturn in consumer spending affects profits in the DIY and gardening sector.
In May, parent company Kingfisher revealed that B&Q had suffered a 7.7% fall in like-for-like sales in the first three months of the year.
Mr Cheshire said the Eastleigh-based company was facing a tough retail environment.
"We need to streamline the business to focus on supporting stores and serving customers," he said.
"The restructuring is about making our plan for the future work, as well as well as being driven by the need to cut costs."
A recent report suggested the boom in home improvements was cooling with the consumer slowdown hitting the market.
Retail analyst Verdict said that spending on DIY and gardening would fall 1.6% to £16.4bn in 2005 - the first contraction in five years.
B&Q still has a 24% share of the market although the company is facing increased competition.