The area's two MSPs - Margo MacDonald, of the SNP, and Tory Lord James Douglas Hamilton - have backed campaigners' demands for a public inquiry.

Sarah Boyack: Gave approval

At a news conference in the Scottish Parliament, they said that when the Scottish Transport Minister Sarah Boyack approved the project earlier this year, she did not know the full facts about the geology.

Since then, a large crater had opened up, close to the route, they said.

A spokeswoman for the Scottish Executive said the minister had acted on the information available and it was now a matter for Midlothian Council.

The local authority insisted the state of the ground had already been taken into account.

Ms Boyack was criticised by opponents for refusing to "call in" the application. They said it was contrary to her policies on controlling traffic growth.

Campaigners are worried about the environment

In March, environment campaigner Joan Higginson said: "The area has been taken care of by the local people.

"They have got together with the Scottish Wildlife Trust and the Green Belt Trust and taken care of it for the last 10 years.

"It is a site for birds, trees and little plants that are starting to regenerate.

"We feel that the tranquillity will be lost because a road will ruin what we have created."

But Midlothian councillor Russell Imrie said it was vital to come up with a "balanced development" which would produce the right kind of infrastructure to aid the growth of the biotech industry.