Rail commuters are suffering delays and cancellations to services because sick leave among conductors has doubled in the past five months, it was claimed today.

Arriva Trains Northern said absenteeism has increased 100 per cent since the start of strike action by the National Union of Rail, Maritime and Transport Workers (RMT) in February.

It has led to a growing problem of cancellations and delays because of staff shortages on services across the district.

And the company says it is impossible to find replacement staff in time to man its trains because it is only informed of the absences at the last minute. "This is affecting our services on strike and non-strike days alike," said an Arriva spokesman. "It is very difficult for us to make alternative arrangements when we are informed of sick leave so late on."

But today the Rail Passengers' Committee (RPC) watchdog said the problem was more likely to be due to the ban on overtime working which has been placed on conductors. It was introduced to prevent striking workers from making-up time lost in industrial action on non-strike days.

Ernie Preston, secretary of the RPC, said it prevented conductors who were coming to the end of their shifts from covering for those on sick leave.

"This excuse is a load of rubbish," said Mr Preston. "If their conductors were allowed to work overtime then there would not be a problem."

Mr Preston said the RPC is planning its own survey on cancellations and delays to Arriva's services and the reasons for the disruption. It has been claimed the ban is causing dozens of services to be scrapped and many more to be abandoned mid-journey because conductors have come to the end of their shift.

Mr Preston said he was personally affected by the ban earlier this week when a service from Leeds to York terminated at Harrogate because there were insufficient staff to continue the journey.

"Until we see the data we can only say this is a potential problem, but there are stories and anecdotal evidence that trains are being cancelled," he said.

The latest performance data was for the period from January to March and showed that 81.2 per cent of Arriva services arrived within five minutes of the scheduled time and 1.3 per cent of services were cancelled.

Arriva's own data for June and July show that cancellations are now running at between 1.4 and 1.7 per cent.

The Arriva spokesman said overtime was not an issue because the company had "more than enough" conductors to cover the required shifts.