A row has broken out between Tesco and a London planning authority over a breach of planning law.

At least two Tesco stores are being investigated by Hounslow council in west London. The authority is concerned about the construction of mezzanines, which, under new planning rules, may have required permission.

A council spokesperson said the planning department suspected that the mezzanine floors at outlets in Richmond and Osterley, were unlawful.

The new rules mean that mezzanines with a floor area of more than 200m2 need planning permission, unless construction had started before May 2006.

Mezzanine floors are extended balconies between the main floors of a building. They were popular with large retailers and supermarkets because they could almost double floor space without applying for permission to extend the existing building.

The spokesperson said: “Tesco said it didn’t need planning permission to build the mezzanines and provided a certificate to show it was lawful. We rejected that as we felt there wasn’t enough evidence.”

The spokesperson added that the council was waiting for Tesco to provide further evidence that construction had started before May 2006.

Tesco said it didn’t need permission, but there wasn’t enough evidence

Hounslow Council spokesperson

Industry sources claim that problems with mezzanines are widespread in the industry.

Many retailers rushed to start work before the cut-off date last year but authorities are now asking for proof that sufficient work was undertaken before then.

A source at the council said: “Hammering in two nails doesn’t count. This is where the stores are finding themselves in breach of the new laws.”

A Tesco spokesperson said: “We are in regular discussions with Hounslow council over the two sites but we’re hopeful the outcome will be satisfactory for all parties.”

He refused to comment on the claim that the problems were more widespread.