Retailers have less than six months to grab extra outof-town floorspace, before planning rules restrict their ability to install mezzanines at existing stores.
Planning Minister Keith Hill is expected to rush through the powers, possibly by the end of this year, subjecting mezzanines to planning controls for the first time.
Hill was expected to take up to 12 months to introduce the secondary legislation. It is a late addition to the Planning and Compulsory Purchase Act, which received Royal Assent last month, following Asda's brash proposals to roll out its mezzanine format.
Retail planning experts suspect Asda's recent High Court battle with Eastleigh Borough Council, which confirmed the supermarket giant's ability to install a 50,000 sq ft (4,645 sq m) mezzanine at its Chandler's Ford store in Hampshire, has added urgency to the Government's plans to control mezzanines.
In the period before the secondary legislation comes into force, the High Court decision has reaffirmed that mezzanines do not require approval where their control was omitted from original planning permissions.
Eastleigh Borough Council leader Keith House said: 'Eastleigh's efforts to challenge the existing arrangements have helped to highlight the problem and will hopefully encourage the implementation of changes sooner rather than later.'
Fleet-footed retailers will have a limited time to act. A spokesman for the Office of the Deputy Prime Minister said: 'There is still a grace period in which people can build mezzanine floors.'
Shopping Park Investors Forum chairman Martin Clews said the Eastleigh decision was 'unfortunate timing', having reignited the controversy in advance of consultation over the secondary legislation.
Asda is now seeking to replace its 30-year-old Chandler's Ford store, with its High Court-backed mezzanine capability, with a two-level store boasting a 95,000 sq ft (8,825 sq m) sales area.