Caledonian Sleeper services are to be cancelled for two days due to staff strike action.

Workers will begin industrial action on Sunday amid claims the rail service's operator "blocked progress in talks".

RMT is arguing that staff have been placed under "intolerable pressure" due to the "mismanagement" of the service.

On Tuesday, the union confirmed the previously announced industrial action would go ahead after a meeting on Monday failed to end in an agreement.

RMT said Serco seemed "quite happy to leave their staff hanging out to dry".

Union members have been told not to book on for any shifts between 12pm on Sunday, September 29 and 11.59am on Tuesday, October 1.

Additionally, members have been instructed not to work any overtime or rest days, not to perform higher grade duties and to work to their original job description from 12am on Wednesday, October 2 onward.

After strike action was confirmed, a statement on the Caledonian Sleeper website said services on Sunday and Monday would be cancelled.

It said: "We have been advised by the Rail, Maritime and Transport Union (RMT) that their members intend to take strike action on Caledonian Sleeper services next week.

"Whilst we remain in discussions with them to try to avoid a strike, if it does go ahead all of our services departing on Sunday September 29 and Monday September 30 will be cancelled.

"We apologise to all of our affected guests for the inconvenience this will undoubtedly cause."

The company added: "We are in the process of arranging alternative transportation with other train operators. "We will confirm the details of this here as soon as we can. "We will of course be processing refunds for all affected guests."

Mick Cash, RMT general secretary, said: "The union is angry and frustrated that promises made to us to address the serious concerns of the Caledonian Sleeper staff have not been honoured and the failure of Serco to come up with any serious progress in key talks yesterday leaves us with no choice but to go ahead with our industrial action exactly as planned.

"‎RMT members have been put under intolerable personal stress as a result of the company's mismanagement of the sleeper service.

"They know it, they have promised to do something about it but they have failed to deliver.

"The move to strike action is entirely Serco's fault and the public will understand that. Everyone knows that when it comes to failure they are global specialists.

"The union remains available for genuine and serious talks but the ball is now firmly in Serco's court."

When RMT initially announced its strike plan earlier this month, Serco's managing director of the Caledonian Sleeper stated that the industrial action was "completely unnecessary".

Ryan Flaherty said: "We are deeply disappointed and frustrated at this industrial action by the RMT, but most of all we are bemused as they have been unable to explain what will bring this dispute to a resolution."