Legislation is the only way to force commercial clients into building green offices, a top quantity surveyor said last week.

Speaking at the British Council for Offices' Greening Commercial Property conference, Davis Langdon & Everest senior partner Paul Morrell said: "Most people are building for profit. There is no commercial benefit for them stepping out of line and building green."

A senior DETR official said there was nothing that could be done by government except to tighten the Building Regulations.

Wide-ranging changes to Part L of the regulations have been proposed in consultation, but experts agree that any changes will be radically watered down before being incorporated next year.

The only other measure that might help, added the official, was a tax on the extraction of aggregates, which is being considered. Morrell said proposals to reform Part L were a step in the right direction but the government had to introduce tax breaks, grants or legislation to persuade clients to build green.

Morrell also criticised the government's preferred way of measuring green construction. He said assessing the amount of carbon dioxide a building emitted per m² of floor area was misguided.

Morrell said this analysis did not take transport issues into account. "We need very serious government-funded research to establish the best methods for measuring greenness," he said.

The DETR official said the government was considering new green indicators and would be discussing changes at a workshop early next month.