Representatives of the Campaign for Borders Rail were reassured by Mr Stewart at a meeting held via video-link that ministers at Westminster remain committed to push for such an extension of the 30-mile Edinburgh-Tweedbank track.
Mr Stewart, MP for Milton Keynes South in Buckinghamshire, said afterwards: “It was great to meet with the very passionate campaigners at the Campaign for Borders Rail.
“They have put forward a very strong case for reopening the line to Carlisle.
“I was delighted that we were able to confirm that the work on the feasibility study will be beginning in the Carlisle area during September.
“I will be pushing this project from within government and will be discussing with my ministerial colleagues across government how we will drive it forward.”
Last week’s discussion was arranged by Berwickshire, Roxburgh and Selkirk MP John Lamont, and he said: “This was a really positive meeting.
“It was a great opportunity for the campaign group to highlight the benefits of extending the railway would bring to our local economy in the Borders.
“Mr Stewart provided us all with an update, and I am delighted that the feasibility study will be starting very soon.
“The benefits that this project will bring to places like Hawick and Newcastleton will be significant and completely transformational.
“Connecting more Borders towns to transport hubs in Carlisle and Edinburgh will greatly improve our links to other parts of Scotland and the UK.
“However, the real benefit I believe will be in the employment and educational opportunities that this would open up for our young people. Too many are forced to leave the Borders in search of better opportunities elsewhere.”
Campaign vice-chairperson Marion Short added: “Meeting Iain Stewart emphasises again that this campaign has significance across every political portfolio.
“Bringing a railway back through Hawick and on to Carlisle sends a clear message of faith in the communities and commerce of the Borders.
“A through route for passengers and freight not only adds resilience and capacity to the network nationally but also helps unlock the economic potential of the entire region.
“Unifying the markets on either side of the border by establishing a new cross-border route will stimulate investment, particularly in housing, employment and tourism.
“These were all points readily acknowledged by the minister, with whom we will certainly look to continue to work with on behalf of the whole Borders community.
“Of course, there is still a long way to go, and our work is by no means done.
“We must continue our current momentum and keep up the pressure on decision-makers.”
Taking part too were fellow campaign officials Simon Walton and Nick Bethune, Penrith and the Border MP Neil Hudson and Carlisle MP John Stevenson.
Also flagged up at the virtual meeting was the possibility of seeking finance from a fund launched by UK transport secretary Grant Shapps in January to support the reopening of rail lines closed in the 1960s such as the Waverley Route from Edinburgh into Cumbria.
Given that its budget is only £500m and it’s already attracted 50-plus bids, it’s unlikely that campaigners will be pinning their hopes on that potential source of funding to cover much of the cost of reinstating the near 70 miles of the Waverley Route not reopened five years ago, however, especially seeing as the price-tag for such an extension is estimated to be upwards of double the £353m the present track to Tweedbank cost.