More than 300 jobs will potentially be lost as the shops shut over the next 12 months.
The affected stores include one at The Fort Shopping Park, Birmingham, which is set to close on February 26 with 31 jobs going; Redditch on May 21 (30 jobs) and The Lower Parade, Sutton Coldfield on June 25 (22 jobs).
Each store will have a 30-day consultation period, while permanent recruitment in the vicinity of each site will freeze.
Roger Jenkins, GMB national officer, said: "These closures are devastating for Wilko workers and the communities who use them.
"It’s yet another nail in the High Street’s coffin and GMB calls on councils and landlords to review commercial leases and offer lower rents.
“Empty high streets and shopping centres are in no one’s interest and but with 400 shops a week closing, this is inevitable - unless the costs of premises can be reduced.
“GMB will now meet with Wilko members to discuss our next steps.”
Worksop-based Wilko currently has 414 stores in the UK including many in city and town centres across the region.
The home and garden retailer said it was undertaking a complete review of its store portfolio and is proposing to close up to 15 stores before January 2023 as leases end and where favourable terms cannot be agreed.
It said it did not impact on its new store or store relocation programme which will continue as planned.
In Shrewsbury it is switching from one town shopping centre to another – paving the way for redevelopment of its former site.
Wilko will relocate from the Pride Hill Centre to Darwin Centre this year.
Jerome Saint-Marc, Wilko chief executive, said: “Our history is steeped in serving our customers and communities going back to 1930 but there’s no denying the way people shop with us and where they want to shop with us is changing. As a business we’re evolving and this includes working with landlords for more favourable terms, as well as looking at locations and store formats. We’ll continue to pull together to make our business better to secure the future of over 16,000 team members.
“We’ll be doing everything we can to support our affected team members who will be offered any available positions in nearby stores. We apologise to those communities where stores are closing but will continue to offer them everything they need in nearby stores or via Wilko.com.”
Of the 15 stores marked for closure, 11 have an alternative Wilko within a five-mile radius.
Other planned closures include Shipley, Bournemouth, Stockton, Scunthorpe, Grantham, Rotherham, Skegness, Llanelli, Merthyr Tydfil and Cleethorpes.