The Waverley Route Trust campaign group has pulled out of talks on enhancing reopening plans for the rail line.
The campaign group has walked out of Waverley talks
It claims that the Waverley Railway Partnership, led by Scottish Borders Council, has no intention of taking on board any of its proposals.
The trust called talks with the promoters of the bill to reopen the Waverley line a "smokescreen".
The railway partnership expressed disappointment at the move and said it recognised many of the trust's points.
Trust chairperson Petra Biberach said they felt they had no choice but to end discussions.
"If the partnership is unwilling or unable to treat seriously our key ideas first advanced more than three years ago, there is simply no point in having any further meetings," she said.
"Our considered view is that from the perspective of the partnership, the current dialogue is nothing more than a smokescreen to satisfy the bill committee."
In addition she said that plans for six stops in the last 12 miles to Edinburgh would result in the Borders getting one of the slowest rail services in the east of Scotland.
David Parker, the leader of Scottish Borders Council which is promoting the bill, expressed disappointment at the withdrawal from talks.
He highlighted a number of points which he said the partnership had taken forward from the trust.
These included the provision of a station at Stow, reduction in journey times, community involvement and heritage trips.
Mr Parker said it was impossible to incorporate any more elements without complete resubmission of the Waverley Railway (Scotland) Bill.
"It is now the partnership's intention to turn its full attention to the final weeks of the consultation process and to the bill's passage through parliament," he added.
MSPs agreed last year in principle to back the reopening of the Waverley railway line between Edinburgh and the Borders.
Scottish Borders and Midlothian councils got approval for a bill authorising the 35-mile line which would cost an estimated £150m.
The previous line closed more than 30 years ago.