That call follows Campaign for Borders Rail officials meeting transport minister Andrew Jones at Westminster last week.
It is now six weeks since the UK Government announced that it would back a full feasibility study into extending the Edinburgh-Tweedbank line to Carlisle as part of the £345m Borderlands growth deal, expected to be signed off next month, but it claims ministers at Holyrood have yet to give such a move their backing.
If they do, a feasibility study could get under way before the year is out, and Mr Jones, MP for Harrogate and Knaresborough in North Yorkshire, told campaign chairman Simon Walton, vice-chairman Marion Short and secretary Nick Bethune that he would urge them to get on board.
Berwickshire, Roxburgh and Selkirk MP John Lamont was also present, and he said: “I was pleased to welcome Simon, Marion and Nick from the Campaign for Borders Rail to Westminster.
“They have done a huge amount of work to keep the momentum behind bringing the Borders Railway to Hawick, Newcastleton and on to Carlisle.
“It was useful to get another commitment from the minister that the UK Government understands the need for this full feasibility study.
“Given that the Scottish National Party promised a full study back in 2016, I’ve been surprised by how quiet they have been on this issue.
“As time goes on, the Scottish Government are under increasing pressure to catch up and back this full study so that we can get on with the next stage of extending the Borders Railway.”
Mr Walton said: “We were delighted to have the opportunity to have a meaningful meeting with the transport minister to discuss the extension to Borders Railway.
“It was great to get the opportunity to seek further relations between the Scottish Government and the UK Government.
“The Campaign for Borders Rail looks forward to the minister initiating discussions with his Scottish Government counterpart.
“We see this as a way to bring to the national agenda the strategic importance of this new cross-border link and the economic benefits that it would spread across the Borderlands, and throughout the UK.”
The Scottish Government insists the blame for any hold-up in delivering the feasibility study promised by its first minister, Nicola Sturgeon, during a visit to Hawick in March 2016 lies south of the border however.
Midlothian South, Tweeddale and Lauderdale MSP Christine Grahame said: “This feels a lot like smoke and mirrors from Mr Lamont.
“The Scottish Government recently published the Borders transport corridor study, giving two route options for extending the railway line in a pre-appraisal.
“However this only covers the extension to the border to the border with England, and the UK Government has yet to undertake pre-appraisal on its side of the Border, which must be done before a feasibility study can go ahead. I’ve yet to see any solid commitment from it on this.
“The Scottish Government is supportive of extending the line and will fully participate in discussions on how this can be achieved.
“The SNP has always backed a feasibility study for the Borders Railway extension and has made a significant investment in the economic development of the Scottish Borders since being in government.
“I’m glad Mr Lamont has come round to supporting the Borders Railway, given his initial outspoken opposition to it. Perhaps he could go back to his Tory bosses in London and persuade them to get on with undertaking their part of the pre-appraisal.”
The study produced by consultant Jacobs UK for the Scottish Government in March includes proposals to extend the Borders Railway east to Berwick or south-west into Cumbria among 21 options now being considered by ministers.
Extending the £353m line, opened in September 2015, to Hawick, via Melrose, would add about 17 miles to its current 30-mile length, and carrying on to Carlisle, via Newcastleton, recreating the old Waverley Route closed in 1969, would require another 50-plus miles of track on top of that.