Planning consultancy Roger Tym & Partners, part of Peter Brett Associates LLP, secured planning consent on behalf of the retailer.
Peter Brett Associates also carried out the transport planning and engineering work for the application.
The store will be the first in the North West to operate the new Next Home & Garden concept, following the opening of its Home & Garden store in Shoreham in August 2011.
Work has started on site, and the store is due to be completed in August.
The extension will trade over two floors selling furniture and furnishings alongside enlarged ranges of bathrooms, kitchens, DIY, decorating and flooring.
The store will be linked to the existing fashion store by a conservatory, coffee shop and outdoor garden centre positioned between the two buildings.
Next has entered into a local employment agreement to recruit 100 staff for the store extension.
Next plans 19 similar centres in the next four years, including at Cardiff and Ipswich.