Weymouth-Waterloo train operator South Western Railway is set to renegotiate its franchise position after less than a year of operation.

The move could threaten improvements to services and planned investments.

A document that has been filed with the Office of Rail and Road regulator, states that SWR and Network Rail have clashed over several elements in the franchise including operational and financial implications of the scrapping of the proposed timetable changes due to be made in December which would have seen more seats and faster journeys between London Waterloo and Weymouth.

Other elements include the engineering work needed and the impact on the power supply which would need to be delivered as part of a planned timetable improvement.

South Western Railway made a pledge prior to its franchise which would see more than £2.4bn of investment in enhancing services across the franchise.

In the report, the ORR said: “Recent correspondence between NR and SWR has highlighted there are several important issues outstanding with SWR’s application.

“We have advised NR and SWR to continue discussions in order to reach agreement on as many of these issues as possible."

John Larkinson, the ORR’s head of railway markets, added: “Given the scale of the uncertainty and disagreement between SWR and Network Rail so far, we have not been able to make significant progress.”

Jeremy Varns, campaign coordinator at South Western Railway Watch said that it “cannot be possible” for SWR to renegotiate their contract.

Speaking to the Dorset Echo, he said: “ This renegotiation was inevitable following the decision to indefinitely postpone the improvements to capacity and the additional services that were promised when the franchise decision was announced in 2017.

“We are now calling on the government to take back control of South Western Railway via its Directly Operated Railways (DOR) management company which would allow Network Rail and the Department for Transport to assess the impact of the proposed new timetables on the network and to put measures in place to ensure their implementation will be a success.

“The government and the Department for Transport are primarily to blame for the mess on our railways. It cannot be possible to allow a company including SWR to renegotiate the terms of their contract; it undermines the entire system and encourages potential franchisees to overbid as we saw recently with Stagecoach and Virgin on the East Coast mainline.”

Ian Girling, chief executive of the Dorset Chamber of Commerce, said: “An effective rail network is essential to a modern economy.

“We would hope that South Western Railway would stick to their original intentions and made the investments as originally promised.”

The announcement also comes after chief executive Tim O’Toole resigned as chief executive of the company in May following news that it had fallen into £326 million of debt.

South Western Railway (SWR) and First Great Western also announced that changes to the winter timetable had been suspended following the chaos which came after schedule alterations on May 20 earlier this month while the companies guards will strike for eight days across the next few weeks in a despite over their role on trains.

Steve Chambers, from Campaign for Better Transport, said: " Passengers will be disappointed and angry at this news, especially as there is no indication of when, if ever, they might expect to see the improvements they've been promised.

"This is yet another knock-on effect of May's timetable fiasco and the mismanagement of the railways. It also highlights an inherent problem with the franchising system where train operators are allowed to win bids based on a promised service that they then frequently fail to deliver.

"We want to see a full independent review of the way in which the Department for Transport manages franchises, including ways in which local authorities, passengers and communities can have a greater say over local rail services."