Andy Burnham, the mayor of Greater Manchester, has written to the transport secretary urging her to require Avanti to increase services between Manchester and London by the end of the month – or remove its contract.

But one rail expert warned that stripping Avanti of the franchise would not necessarily lead to an improvement in services, as it would not solve the shortage of drivers.

In a letter to Anne-Marie Trevelyan, Burnham said the company’s plans to wait until 11 December before returning to an increased timetable would cause too much disruption to passengers and damage to the Greater Manchester economy.

He called for a consistent service of at least two trains per hour between Manchester and London by the end of October as a staging post to a return of three trains by December.

If the company were unable to make this commitment, Burnham argued, the company’s contract should be terminated when it is considered for renewal next week.

It is now more than six weeks since Avanti West Coast reduced services between London and Manchester to mostly just one per hour, although additional services have since been added at the busiest times.

The company promised the move would bring “stability and certainty” for passengers – but an average of 10% of Avanti West Coast services between Manchester and London over the last three weeks were either cancelled or significantly late. Over the same three-week period, 27% of services failed to arrive on time.

The problems are not limited to passengers going from Manchester to London. As a result of the cuts, there is now just one direct train each day from London to Holyhead, the Anglesey gateway for ferry services to Ireland.

Earlier this week five Conservative MPs from Welsh constituencies wrote to the rail minister, Kevin Foster, to call on the government not to renew Avanti’s franchise. The service has become “deplorable”, the MPs said.

But one expert warned that stripping Avanti of the franchise would not necessarily lead to an improvement in the service.

Dr Tom Haines-Doran, the author of Derailed: How to Fix Britain’s Broken Railways, said: “The problem is a lack of drivers … [and] leaving the service even more reliant on overtime working. When waves of Covid cases are thrown into the mix, the result is an unreliable service. The problem is that, while it is easy to quickly cut staffing to save money, it takes a very long time to build it up again.

“Training drivers takes a long time. Even recruiting drivers from other companies is no quick fix, as it takes months to accumulate ‘route knowledge’, which is vital for safe operation. Whether it’s the government or Avanti running the franchise, it’s going to be months before services are back to anything like the three trains an hour which passengers were used to.”

An Avanti West Coast spokesperson said: “Our revised timetable, with no reliance on overtime, is proving more reliable – in the last week we have run 300 trains between London and Manchester, with approximately 1 in 30 of them cancelled, mainly because of short-notice sickness. That compares with 1 out of 13 trains cancelled back in mid-July.

“We are already delivering on our commitment to increase the number of services we are running between Manchester and London, with 3 or 4 trains an hour departing Manchester Piccadilly at the key times of the day.

“Nevertheless, we know that at the moment we’re not delivering the service our customers rightly expect and we apologise for the enormous frustration and inconvenience this is causing. We would like to thank our customers for their patience and understanding.”

The Department for Transport said: “The government will consider all options when Avanti West Coast’s contract expires on 16 October.”

It added: “The problems facing Avanti are a prime example of why we need to modernise our railways, so passengers benefit from reliable timetables that don’t rely on the goodwill of drivers volunteering to work overtime in the first place.”

• This article was amended on 11 October 2022 to add a comment from Avanti West Coast and to clarify that additional services between London and Manchester had been added at the busiest times. It was also revised to remove a comment from Dr Tom Haines-Doran that Avanti had chosen to reduce its spending on drivers. The last point, which was disputed by the company, was intended to convey his fuller view that Avanti had failed to invest in the provision of drivers for the level of service it was required by contract to run.