SUNDAY train services between Glasgow and Edinburgh will double in frequency from September as ScotRail extends its half-hourly service on the busy route.

An additional 12 trains a day will be laid on from September 9, the highest frequency operated on a Sunday in the 170-year-old history of the main line via Falkirk.

The move comes amid a boom in demand for rail travel, with passenger numbers higher than at any time since the 1920s, and follows the trial of a half-hourly Sunday service during the last Edinburgh festivals.

The half-hourly service will be extended throughout the day. At the moment it is only available between 1pm and 9.30pm.

The announcement was greeted by business and tourism leaders.

Scott Taylor, chief executive of Glasgow City Marketing Bureau, said demand for rail travel between Scotland's two biggest cities had been driven by a combination of factors.

He said: "We know that hotel occupancy is going up, spending is going up and air capacity is increasing, which is bringing a lot more visitors to Glasgow."

Glasgow Chamber of Commerce deputy chief executive Richard Muir said: "We welcome this increase in services between Glasgow and Edinburgh, with the two cities combined being the second most significant economic region in the UK. Ongoing improvement in connectivity between these two key economic cities can provide real benefits from a business and tourism perspective.

"It is also encouraging to see further commitments being made to Glasgow as part of the country's rail improvement programme. We will continue to campaign for further improvement in connectivity to and from Glasgow which we see as a key future economic driver."

Regarded as the jewel in the ScotRail crown, Edinburgh-Glasgow is thought to be one of the few profitable routes in the network, with 6.8 million passengers last year, accounting for around 8% of the total number carried by the train operator.

A ScotRail spokesman said the new timetable had been drawn up in response to feedback from customers.

Steve Montgomery, ScotRail's managing director, said: "We recognise people's travelling patterns continue to change and these new, more frequent services offer even more opportunities for people to make the switch to rail, delivering environmental and economic benefits for Scotland."

Transport Minister Keith Brown added: "I am delighted to welcome ScotRail's announcement of a record number of Sunday services on this key route.

"The shift from road to rail travel is hugely important in meeting the ambitious climate change targets set by the Scottish Government. But travelling by train is also a fantastic way for people to get around and enjoy what Scotland, and her two biggest cities, has to offer."