Disability campaigners, who believed they were dealt a winning hand in the fight for equality of access to public buildings, are finding they have been trumped by planning legislation, a leading law firm revealed last night.

The Disability Discrimination Act, which became law last October, compels the owners and occupiers of buildings to which the public have access to make provision for people with a range of disabilities. In extreme cases, major structural and organisational alternations are needed to accommodate the disabled.

But although the new law seems tough on the surface, underneath it lacks real teeth, according to Katherine Campbell and Rebecca Warren, associates in the Midlands office of international law-firm Reed Smith.

They say that although the Act was passed with the best of motives there have been unexpected problems in the way it is implemented.

"Modification to buildings - to provide wheelchair access, for example - may require planning permission," said Mrs Warren, a planning lawyer in the firm's Midlands office.

"In addition, because many of the buildings concerned are listed, listed building consent may be needed. Whether or not alterations are considered acceptable for a specific listed building often depends on the views of the officer taking the decision, and that means inconsistent approaches between different local authorities.

"If planning permissions or listed building consents are refused, this would mean that planning law will override the Disability Discrimination Act."

Many government and local authority buildings - along with banks and other establishment structures - operate out of grand old buildings which have long been considered important to Britain's architectural heritage.

The same goes for cultural and historic buildings - such as Shakespeare's Birthplace in Stratford-upon-Avon - where alterations to the fabric would be clearly considered as an act of desecration.

Mrs Campbell, a property litigation lawyer, said: "It is an interesting debate - do we make our old buildings serviceable and compliant with modern requirements, or wrap them in mothballs and keep them the way they are?

"The way the DDA has been drafted means that planning refusal is a perfect defence for a property owner or tenant who doesn't make access available for the disabled.

"Unfortunately, in order to get the official refusal, the luckless owner could have to incur architects' costs and other expenses running into thousands of pounds, because the law says you have to take 'reasonable steps' to make your building compliant.

"Many will just go through the motions, knowing the result in advance, simply for the apparent immunity that a planning refusal will give."