Rail commuters could face further disruption in the new year with news that staff at First Great Western are to vote on strike action.

The company's new timetable, launched last week, has seen dozens of trains cancelled due to a lack of drivers or guards, despite staff putting in many hours of overtime.

The drivers' union Aslef and the RMT, which represents train managers and conductors and some drivers, have called ballots of their members at FGW after what both unions said was "a breakdown of industrial relations".

The dispute has been exacerbated by the use of managers to operate some trains due to the staff shortages.

The train crews are being asked whether they would support strike action, or action short of a strike. Both ballot results will be declared on Wednesday, January 10.

Aslef district organiser Dan Moran said: "For over two years Aslef has been telling First Group that they were short of staff, of drivers and of train managers. They denied this.

"We feel sorry for the public, who pay our members' wages. They have had abysmal service from FGW."

Aslef has a short-term agreement with FGW that drivers will be available to work overtime on rest days, while recruitment of new staff takes place, but this deal is due to expire on December 29.

Mr Moran said: "We're still negotiating on rest day working. There is a meeting on December 28, to see if we can extend the agreement into January."

FGW's chief operating officer Andrew Haines admitted staffing was a problem in a letter on Wednesday apologising to passengers for poor performance in recent weeks. He said the firm was recruiting and training 40 more drivers and 60 guards.

However, Mr Moran warned that it would be some time before they were ready for work. He added: "You can't pluck them out of the air. It takes a year to train a driver.

"They are least 100 drivers short in Aslef's view.

"I have met Andrew Haines and believe he is genuine about tackling the problems, but is it too little, too late?"

He said that Aslef wanted to see FGW taken back into public ownership, and turned into a showcase nationalised railway.

Derek Potter, the chairman of the Cotswold Line Promotion Group, which represents passengers on the Oxford-Worcester route, said: "I sense that the guards and senior conductors are not a happy bunch at the moment.

"The breakdown may be due to there not being enough staff and I understand that retraining in operating HSTs and new stopping procedures is proving difficult.

"I suppose there may be a feeling of frustration that what is meant to be an enhancement - using more HSTs - is causing a lot of extra work."

In a statement, FGW said: "We understand that the RMT is planning to ballot its members about the possibility of industrial action, but we cannot comment further until the results of any ballot are known.

"We are working with unions to find a resolution to any issues they may raise."