This morning, Mr Lamont said he intends to vote against the agreement as it currently stands, saying it does not deliver for the Borders, Scotland or every part of the United Kingdom.
It is widely expected that the agreement will be rejected by MPs and there is speculation that the vote may be delayed to give Prime Minister Theresa May time to go back to the EU and try to renegoatiate a better deal.
In a statement to constituents, published today, the MP said that after “carefully considering the agreement in detail” he has “reluctantly” come to the view that he cannot support the deal as it currently stands.
In his statement, Mr Lamont says: “I have never doubted the Prime Minister’s commitment to deliver the best for this country.
“Even amongst those who do not support this deal, the vast majority of people recognise she has put her heart and soul into public service over the past few years. And she has had an almost impossible job to do.”
Mr Lamont was criticised on our Facebook page last week as he revealed he had yet to make up his mind, struggling between his loyalty to Mrs May and his doubts over the terms of the deal she had brought to the table.
However, he seems to have come to a decision over the weekend.
Setting out his reasons for voting against the deal, Mr Lamont said: “In coming to my decision, I have had to weigh up the risks associated with the agreement, with the risks of the unknown.
“There are clearly significant risks associated with this withdrawal agreement, including the potential that fishing could be traded away and the possibility that we will be locked in to the backstop arrangement.
“This deal could mean that we retain some of the worst things about EU membership without being able to take advantage of the opportunities of Brexit. The UK could end up in an uncomfortable halfway house – having to follow EU rules without any influence or say over them.
“I have come to the conclusion that on balance, these are not risks I am prepared to take.
“I want the UK to move on and be able to focus on other, more important things. This withdrawal agreement could mean that we are still talking about Brexit for many more years to come.
“Over the past few weeks I have received upwards of 1,000 emails, social media comments, survey responses and phone calls from Borderers.
“While there is little consensus about what should happen next, the clear message that I have received from my constituents was that this agreement does not satisfy many.”
The Borders’ other MP, Scottish Secretary David Mundell, continues to back Mrs May’s deal.
He has said he was forced “to make a judgement” on the issue, despite him previously stating he would not support a plan that set different arrangements for Northern Ireland after Brexit.
And the deal on the table includes a “backstop” which many believe would see Northern Ireland being in a better trading position than Scotland.