Local MP Alister Jack supported Prime Minister Theresa May's Brexit deal in a speech during the historic EU withdrawal debate.
The Dumfries and Galloway representative at Westminster told Commons colleagues that he had reached his decision after 'much deliberation.'
He concluded the deal could deliver for all the UK without undermining the integrity of the Union.
Mr Jack said: "It is a pragmatic compromise that means we leave the political union, the customs union, the Common Fisheries Policy and the Common Agricultural Policy.
"It ends free movement and the jurisdiction of the European Court of Justice over the UK.
"It is also the deal that reflects the closeness of the referendum result by leaving the EU at the same time as protecting our jobs and economy."
Mr Jack, who originally expressed reservations about the so-called Northern Ireland border backstop, concluded that the controversial aspect of the deal would not undermine the integrity of the UK.
He pointed out that Cairnryan, a strategically and important port in his constituency, handled around 45 per cent of Northern Ireland's trade with the rest of the UK.
Mr Jack told fellow MPs: "Any border down the Irish Sea or proposal to carve off Northern Ireland from the rest of the UK would be hugely detrimental to the port, which would be wholly unacceptable."
He stressed that nothing in the withdrawal agreement would prevent the UK from ensuring unfettered access for goods moving from Northern Ireland to the rest of the UK internal market.
The MP welcomed last week's UK Government commitment to enshrine the access guarantee in primary legislation.
Mr Jack suggested the backstop could be avoided as, "with the right level of political will and determination," it was entirely possible to reach agreement on the UK-EU relationship before December, 2020 when the country was due to again become an independent coastal state.