The Treasury has dismissed fears that the planning gain supplement is unworkable despite the failure of three similar land taxes since the Second World War.

Speaking at a British Urban Regeneration Association seminar held last week to discuss the government's response to the Barker review, Treasury officials said the system would be "smarter" than previous efforts.

Mark Fine, tax team senior policy adviser at the Treasury, said: "Previous development taxes were riddled with loopholes and we think we can do a better job."

He confirmed that the government was still interested in local "roof taxes", adding that the Treasury wanted to examine the "interface" between these local levies and the supplement.

He added that by bringing a large number of sites into the supplement net, it would be easier to keep the rate at a modest level.

But planners and property consultants said the supplement, which is currently in consultation, was flawed as a concept. They think the government has erred in concentrating on the large gains that can be made from uplifts in the value of greenfield sites, rather than on the brownfield sites on which it wants to focus regeneration.

Previous taxes were riddled with loopholes. We think we can do better

Mark Fine, Treasury

Gerald Allison, director of strategic development at property consultant DTZ, said he was worried about the viability of small schemes if they were liable for the supplement.

He said: "The planning system does not create a realisable asset. A lot of huge complex projects have a negative value when planning permission is granted."

Lee Searles, planning policy officer at the Local Government Association, said councils preferred section 106 on the grounds that it was locally controlled and more sensitive to circumstances on the ground, unlike the PGS proposals.

"The supplement will not make it easier to sell the benefits of development," he said.