This warning will hit the 25 train operators hard. A spokeswoman for John Swift, the rail regulator, said that the last complete set of figures showed that 45 per cent of calls to the train inquiry service went unanswered.
This is little improvement on figures earlier this year, which showed that 49 per cent of calls were not taken in April and 35 per cent in May.
The regulator's targets state that 90 per cent of all calls should be answered. Mr Swift said there had been no sustained improvement on the "awful" performance of the service in April.
Unless the service improved within 28 days, a final enforcement notice would be issued and fines amounting to hundreds of thousands of pounds imposed on operating companies.
The penalties are severe. Under the fines system, if more than 25 per cent of calls are not answered then train companies will be fined pounds 200,000 per percentage point of calls not taken.
However, the Railways Act does not allow the regulator to fine an operator for the first offence. This means that should the service improve in August - meeting Mr Swift's targets - it leaves him powerless to act.
The train companies had annoyed the rail regulator's office last month by not bringing the failing service to his attention. The regulator now gets a weekly bulletin containing all the figures.
Officially known as the National Rail Enquiry Service, the service is administered by the Association of Train Operating Companies (Atoc).
In April last year, the system had 80 different numbers. These were replaced by a single number in October 1996 and the whole system franchised to the private sector. This has seen call from London answered by operators in South Wales, many of whom are unaware of the local destinations.
Since the autumn, performance had been climbing steadily. A spokesman for Atoc claimed the system was handling nearly "one million calls a week". "We are confident of improving the service," he added.
The railway industry was also chided yesterday by safety watchdogs who called for old-style "slam-door" railway carriages to be phased out, amid concerns over their crash- worthiness. Nearly 2,300 of the Mark 1 carriages, built between 1959 and 1974, are still in regular passenger service.
The carriages are believed to have caused deaths in crashes - including the 1988 Clapham disaster - because of a tendency to "ride over" carriages ahead.
Jenny Bacon, the director general of the Health and Safety Executive, announced yesterday the launch of a consultation exercise which may hasten the phasing out of the carriages.Reuse content