Shopworkers' union Usdaw is campaigning for recognition by Screwfix, Kingfisher's DIY e-tail and mail order business.
Usdaw officials have been demonstrating outside Screwfix's Yeovil headquarters.
A spokesman said: 'Screwfix have not been letting us recruit on-site. We have no agreement with the company and they do not recognise us.'
Screwfix human resources director Richard Butler said: 'We respect Usdaw's right to canvass our staff, but we don't want formal presentations. We think we have a dynamic, fair and supportive business.'
Usdaw aims to sign up enough Screwfix staff to force recognition on the e-tailer.
- Usdaw has called for a higher national minimum wage that would also apply to 18-year-olds. Deputy general secretary John Hannett is arguing for an increase to between£4.84 and£5.38 an hour.