An award-winning conservation architect has warned that Edinburgh is in danger of being crippled by a planning system “terrified of offending” the city’s World Heritage status.

Lorn Macneal told the Scotsman that any alterations proposed for historic homes are automatically blocked by city planners, leaving the properties “blighted” by their listed status and unable to be turned into “workable”, modern accommodation.

He said that “draconian” attitudes which stop homes from being altered for modern living are rendering properties useless for contemporary families.

Edinburgh was granted World Heritage status by Unesco in 1995, offering protection to areas of the city’s medieval Old Town and the Georgian New Town.

But Macneal said modern lifestyle choices for homes need to be considered when planning permission for listed buildings is sought.

“I do not look to discredit a listed building, but merely to ensure this draconian attitude in planning must change,” he said.

“These historic homes were built in response to the socially engineered needs of that period. Time has moved on and yes we must protect the significant parts of these buildings –the frontage, the true principal rooms, the stairwell – but attitudes within the planning system must adopt to allow change in order that these homes may be enjoyed.

“The key question, the prerequisite that every officer should start asking is ‘does this really matter?’ and if it doesn’t then it’s time they really must start letting go.”

He added: “The whole New Town of Edinburgh has evolved over a period of more than two centuries with charm and character.

“We have seen the introduction of projecting shop fronts, an eclectic mix of attic dormer windows, and cast iron balconies. If you ask now to add a dormer window in a street full of them, or a projecting shop front, or anything that may alter the external fabric, then it will be resolutely denied by a system terrified of offending our city’s World Heritage Status.”

He said that there could be two similar villas next door to each other with one forced to conform to listed status requirements and the other free to carry out internal alterations.

“One might have been built by a famous architect on a bad day, so was listed and the other is almost identical but they are free to do what they like,” he said. “It’s madness.”

Councillor Ian Perry, convener of the planning committee of Edinburgh City Council, said: “The World Heritage site should not be seen a barrier to development in the city centre. An economically successful city centre is critical to the future of the World Heritage site.

“It is inevitable new developments will be attracted to the centre, and this is important for the city to evolve. We are committed to managing this process carefully and ensuring that the greatest consideration is given to its historic environment.

“Seventy-five percent of the buildings in the World Heritage site are listed and it is important that changes are made in a way which respects the character of the individual building as well as its part in the wider conservation area. Our Unesco World Heritage Status is something the council takes very seriously.”

The warning follows news that David Black, the first chairman of Edinburgh’s Southside Association, is calling on the status to be removed, saying there had been a series of planning blunders which had destroyed Edinburgh’s historic cityscape.