Seven people were killed in the Potters Bar crash

Jarvis is poised to win the contract to replace track in the London North East Region - which includes Potters Bar in Hertfordshire.

Bob Crow, general secretary of the Rail Maritime and Transport union, said he was very concerned at the news.

"I find it astonishing and disgusting this decision has been made while the criminal investigation is still underway," he said.

"It is an insult to all those people who died and were injured at Potters Bar."

Seven people killed

On Friday, Jarvis was named by Railtrack's successor body Network Rail as the preferred bidder to replace track on the Potters Bar stretch of line.

The track replacement work is separate to Jarvis's overall maintenance contract for London North East which runs from 2001 to 2006.

Seven people were killed and 76 people were hurt when a West Anglia Great Northern train derailed at a set of points just outside the station on 10 May last year, as it headed to King's Lynn, Norfolk.

Ten days after the crash, Jarvis said that sabotage could not be ruled out.

No evidence of sabotage

But an accident report last month from the Health and Safety Executive (HSE) said there was no evidence of sabotage or deliberate unauthorised interference with the points.

The HSE also said earlier inspections had not detected defects in the points at Potters Bar.

Also, the points were not adjusted properly, and there was a failure to understand their design and safety requirements.

Responding to the report, the company said last month: "Jarvis maintained the points in accordance with long-established industry procedures.