A report by the Rail Safety & Standards Board shows that most of the people killed in the two most recent rail crashes died as a result of being thrown through breakable windows. The windows are found on almost half of Britain’s trains.

Laminated glass would cost only £125 per window but train companies are trying to delay making the change as long as possible in order to save money.

Under the industry’s current plan, passengers will continue to travel for at least the next 15 years in trains from which they have a greater risk of being thrown out and killed.

In crashes at Potters Bar in Hertfordshire in 2002 and Ufton Nervet in Berkshire in 2004, 15 people were thrown out of breakable windows. Eight of those died.

In the 95mph crash at Grayrigg in Cumbria in February, the windows of the Virgin train were laminated, preventing anyone from being thrown out despite several of the carriages rolling over. Only one person – an 84-year-old woman – died later in hospital.

Under an industry safety standard, all trains built since 1993 have had to have laminated glass. But the standard does not apply to older trains.

The safety board studied seven fatal crashes in the past decade and found that breakable windows were one of the greatest causes of death among passengers, with 12 dying after being thrown through breakable windows.

In the report, the board said: “Industry and glass experts agreed that laminated glass provided significantly better passenger containment protection in accidents.”

It said that laminated glass would also reduce the risk of injury from “crash debris or other objects penetrating the windows”.

But the board decided that not enough lives would be saved to justify the immediate replacement of all breakable windows. Instead, it recommended that “windows on existing vehicles should be considered for progressive replacement with laminated glass particularly at refurbishment”.

The industry had acknowledged the risk after a crash in Polmont near Falkirk, Central Scotland, in 1984, when 13 people died, several after being thrown through windows.

Peter Webster, who saw his daughter Emily, 14, being thrown to her death in the Ufton Nervet crash, said that she would have survived if the window had been laminated.

“The industry has continually given excuses for not fitting laminated glass because they are trying to save money. But the cost is pretty minimal and it would avoid other families suffering in the same way we have.”

Lawyers for relatives of passengers killed at Ufton Nervet commissioned a report by David Greenway, a rail safety expert and vice-president of the Institution of Mechanical Engineers, into the benefits of fitting laminated glass to older trains.

Mr Greenway’s report, which has been seen by The Times, concludes: “The likelihood of another window-breaking event would appear high and delay in fitting laminated windows would leave a higher than average risk.”

Two companies, First Great Western and GNER, are refurbishing some of their trains and fitting laminated glass. All GNER trains are due to have the glass by 2009. The Association of Train Operating Companies said that there was no deadline for replacing breakable glass in the entire British fleet. First and Stagecoach, two of Britain’s biggest train companies, said that no decision had been made on when laminated glass would be fitted to all their trains.

Mr Greenway found that the dangers of breakable glass were greatest on trains that travel at 125mph (200km/h). Stagecoach, which takes over the Midland Mainline franchise next month, said that it was “looking to fit laminated glass” to its high-speed fleet “in a couple of years’ time”.

Mr Greenway found that Stagecoach could, if it chose to, replace the windows within six months without causing disruption or needing to hire additional trains.

Anson Jack, the safety board’s director of policy, research and risk, said that it had rejected the faster fitment of laminated glass because “it is so much more expensive”.

Mr Jack also dismissed the idea of putting labels on windows telling passengers whether or not they were laminated.

“If you introduced a situation where people were given advice that sitting in a particular part of a coach was more or less safe than another part, based on the very low probability of an incident, there is a likelihood that using trains could become more difficult for people.”

Louise Christian, a lawyer representing bereaved relatives at the ongoing inquest into the deaths at Ufton Nervet, said that the coroner had £125 refused to accept the Greenway report as evidence after being advised against doing so by the rail industry.

“We have to ask why the rail industry parties are trying to suppress this evidence. I think it is because they don’t want to incur the extra cost.”