The accident will add to the industry's woes about safety

The four were killed on the West Coast Main railway line at Tebay in Cumbria when they were hit by a wagon which came loose at a loading yard several miles away and ran down a hill.

Accidents, delays and poor service have long plagued the network and some private firms working on the lines have been accused of sacrificing safety for profit.

Network Rail, the body managing the network, announced in October last year that it would be taking track maintenance back in-house.

It took over from Railtrack in October 2002, a year after the then-transport secretary Stephen Byers put Railtrack into administration following a series of fatal rail accidents.

When Network Rail took track maintenance out of the hands of private firms commentators described it as the biggest reorganisation since British Rail was abolished.

WEST COAST MAIN LINE Upgrade designed to reduce journey times between London, the Midlands, the north of England and Scotland Cost of project has risen to �6bn and suffered delays due to cuts in Network Rail's spending It is one of the UK's busiest rail routes carrying about 2,000 trains per day Pendolino trains which can reach 125mph are due to start "tilting" and hitting top speed along a section of track in September

But last month Network Rail said it was justified in letting private firms continue to work on the rail lines, renewing track.

Lucrative upgrade contracts are due to be awarded this month even though some tenderers were criticised for their track maintenance records after the Potters Bar and Hatfield accidents.

Four people died and 35 were injured in October 2000 after a London-Leeds train travelling at 100mph derailed at Hatfield in Hertfordshire. An investigation blamed a broken rail.

In May 2002 at Potters Bar in Hertfordshire seven people died and over 70 were injured after a WAGN service from London to King's Lynn crashed.

One carriage derailed completely on faulty points and rode on to the platform.

The Strategic Rail Authority was set up in 2001 to let and manage passenger franchises and oversee major infrastructure projects.

Last year it unveiled its long-delayed 10-year strategy to improve the railways.

But the �67.5bn package came as it was reported that many of the train operating companies faced losses of �120m.

The rail improvements were based on a �33.5bn government subsidy with the rest from private investors.

However, many promises made three years ago in the government's 10-year transport plan for comprehensive upgrades to lines have since been dropped.

And train operating companies have begun cutting services as money is too tight.

In addition, a �4bn programme to introduce new trains is failing to proved a better service, the National Audit Office reported this month.

The public spending watchdog said in some cases, the old trains were better because they were more reliable.