Image copyright PA Image caption Serco Caledonian Sleeper launched its new £150m fleet with a promise of a "hotel on wheels"

Caledonian Sleeper staff have voted for industrial action in a dispute over "appalling" working conditions.

The RMT union said members have suffered workplace stress and mental health issues following the introduction of its new fleet.

The union said poor staffing levels and insufficient training had contributed to a complete breakdown in industrial relations.

Serco Caledonian Sleeper said it was "disappointed" by the ballot result.

Members voted by more than 10 to one for strike action and action short of a strike in a turnout of more than 80%, the RMT said.

Serco Caledonian Sleeper launched its new £150m fleet with much fanfare on the lowlander route between London and Glasgow/Edinburgh in April, promising a "hotel on wheels" travel experience.

Media playback is unsupported on your device Media caption The service boasted a "hotel on wheels" experience

But it soon ran into difficulties, with rolling stock having to be taken out of service because of wheel damage and problems with "customer experience".

The roll out of the new trains to the Highland service has been delayed while the company focuses on its lowlander route.

RMT general secretary Mick Cash said: "Our members on the Caledonian Sleeper are sick and tired of paying the personal price for the botched introduction of the new fleet and that is why they have delivered this overwhelming vote for action.

"It is time for Serco to wake up and take note of the appalling working conditions their mismanagement has lumped on their staff and to take action to resolve this dispute.

"The result will now be considered by the union's executive and we remain available for genuine and meaningful talks."

Ryan Flaherty, Serco's managing director for Caledonian Sleeper, said: "We're deeply disappointed by the result of the ballot.

"I believe we have shown a real commitment to dealing with the issues the RMT has raised and indeed there was an acceptance on all sides that progress was being made.

"We remain open and willing to engage in further talks to avoid industrial action and are fully committed to delivering the best possible service to guests."