Berwickshire, Roxburgh and Selkirk MP John Lamont has stated he will not support an opposition attempt to take a no-deal Brexit off the table.
A crunch vote is expected this evening on a bill, sponsored by opposition MPs, which is designed to stop the UK leaving the EU on October 31 without an agreement.
Prime Minister Boris Johnson has said that if MPs support this bill, he would call a snap General Election.
Mr Johnson had also earlier threatened his own MPs that they would be deselected if they rebelled against the government by supporting the bill.
Mr Lamont has slammed SNP and Lib Dem MPs who “claim to want to avoid no deal, but are refusing to back any deal negotiated”.
He said: “The majority of Borderers are democrats, who respect the result of the UK-wide referendum in 2016 and just want Brexit done.
“This bill is simply an attempt by [Jeremy] Corbyn and [Nicola] Sturgeon to take control by the back door and to frustrate our departure from the EU.
“I want the UK to leave the EU with a sensible deal, which is why I twice voted in favour of the only deal on the table.”
Mr Lamont had originally voted against the withdrawal agreement deal struck by then PM Theresa May, saying he had “significant misgivings” about the agreement, citing the lack of clarity about fishing after Brexit among other things.
Now, he says, a no-deal scenario has to stay on the table to allow any other negotiations of the withdrawal agreement to take place.
He added: “This legislation will kill the negotiations stone dead and make achieving a better deal impossible.
“There will be no reason for the EU to agree to any changes to the current deal.
“And there is no guarantee that the EU will agree to an extension, meaning negotiations end and we leave on October 31 with no deal.
“I am increasingly astonished with SNP and Labour MPs who claim to want to avoid no deal at any cost, saying that they will not support any deal negotiated with the EU.
“I will be standing up for democracy and for the majority of my constituents who are sick and tired of Brexit and want the country to move on.”
In the EU referendum of June 2016, 58.47% of Borderers who voted, voted to remain in the EU.