Scotland's train operator has insisted it will be business as usual this weekend as staff walk out for the third time in a month.

ScotRail bosses plan to run their highest number of services yet on Saturday, and insist that all trains will run on key routes.

That includes the main link between Glasgow and Edinburgh, which has added importance this weekend as Scotland take on England in the Calcutta Cup Six Nations match on Saturday.

Members of the RMT union are taking strike action in an ongoing, bitter dispute over who will open train doors on a new link between Edinburgh and Glasgow.

ScotRail plans to run driver-only operation trains, with ticket examiners, when the line between Airdrie and Bathgate opens later this year. The RMT wants full guards to work on the route - something the company says would cost more than £1.4 million.

Steve Montgomery, managing director of ScotRail, said: "It will be business as usual. Our contingency plans are such that we intend to run the vast majority of services."

• Full details of the affected services

The RMT has called for action from transport minister Stewart Stevenson over the dispute. RMT general secretary Bob Crow said: "We are demanding that First Scotrail, Transport Scotland and the Scottish Government get their act together and sort out the direct and meaningful talks that they have promised the public in their media briefings. Those talks have to be at the highest level with the politicians and managers who are calling the shots in this underhand move to axe the guards.

"We cannot allow the current disarray at the top of First Scotrail, Transport Scotland and the Scottish Government to continue. They have already been caught out playing fast and loose with passenger safety and at this rate it is only a matter of time before they have a tragedy on their hands."

A ScotRail spokesman said that the new line would create 130 new jobs and that the trains operating on it were the same as those that had operated in Scotland for 25 years.

The spokesman added: "Nothing changes with the introduction of the new services - where part of the line already has driver door operated trains with a ticket examiner on board. Indeed, the majority of ScotRail journeys are on such trains - almost 47 million journeys a year.

"The protection of the train is the driver's responsibility on all ScotRail services, regardless of the grade of the second person on board - a ticket examiner or a conductor."

While the company is aiming to break the 93% of services that ran on Monday, March 1 - the previous strike day - and will lay on extra carriages for the rugby match, some services will be cancelled or replaced by buses.