Four workmen who were flung 80ft to their death from a motorway bridge were working in a gantry with insufficient brakes while risks to safety were repeatedly ignored, a court heard yesterday.

Darlington-based Yarm Road Ltd, formerly known as Kvaerner Cleveland Bridge Ltd, and Costain Ltd, will be sentenced today, after pleading guilty to breaches of health and safety law at a previous hearing at Bristol Crown Court.

Andy Rodgers, 40, of Middlesbrough, Paul Stewart, 24, of Newcastle, Ronnie Hill, 39, of Glasgow and Jeff Williams, 42, of Newport, Gwent, died when they fell from a gantry while working on the Avonmouth Bridge, which carries the M5 near Bristol, on September 8, 1999.

Philip Mott QC told the court there had been "persistent and blatant breaches" of the law over a long period of time, with safety advice from technical advisors, given only a week before the accident, not acted upon.

The companies had won the contract for the six-year work worth £150m to widen and strengthen the bridge.

But Mr Mott said they had been breaching health and safety law over a long period of time, exposing their workers to danger, as well as people travelling by road or rail under the bridge, and those who lived or worked under the bridge.

The court heard that there had not been sufficient risk assessment carried out, with equipment left untested.

In addition, workmen and supervisors had not been given sufficient training.

He said that there had been warnings, where gantries had moved in an uncontrolled fashion up the slope because of the wind on previous occasions, but that no action had been taken.

A judge can impose unlimited fines for the breaches of the Health and Safety at Work Act 1974, as well as costs which total £525,000.

Yarm Road Ltd, which gave a company address of Hammersmith, west London, was charged with two offences under the act - failing to ensure that persons not in its employment were not exposed to risks, and also failing to ensure the safety of its employees, including Mr Williams, Mr Stewart and Mr Rodgers. It has admitted both charges.

Costain Ltd, of Maidenhead, Berkshire, was charged with one count under the act, failing to ensure that persons not in its employment, including Mr Williams, Mr Rodgers, Mr Stewart and Mr Hill were not exposed to risks, which it also admitted.

Mr Mott said: ''This was an accident waiting to happen."

Wynn Williams QC, defending Yarm Road Ltd, said while the company accepted its failings, this had not been done deliberately.

"The genuine attempt was made, but it fell short of what was required," he said.

Mr Justice Owen said that the case was one of "considerable gravity and some complexity" and adjourned sentencing until today.

Cleveland Bridge was the subject of a management buy- out last year.