West Cornwall MP Derek Thomas said he believed "further compromise" over Brexit could be reached with the EU if tonight's crunch vote in the House of Commons fails.

He has been speaking as MPs prepare to finally vote on Prime Minister Theresa May's Withdrawal Agreement, which sets out a deal for when Britain leaves the EU on March 29.

This includes rules for trade, the rights of European citizens currently living in the UK and vice-versa and the financial contribution that the UK will have to pay the EU to leave - a so-called "divorce settlement."

As things stand, the UK will leave the union on that date regardless of whether an agreement has been reached, with the position simply defaulting to 'no deal' and World Trade Organisation rules would come into force.

Tonight will be the first time that MPs will get to vote on the agreement, after Mrs May postponed one from December 11 at the eleventh hour in order to continue talks with EU leaders.

Mr Thomas has supported leaving the EU from the start, describing the referendum result in 2016 as "the right decision."

However, he said: "If the government loses the Withdrawal Agreement vote there is still time to get the changes we need from EU negotiators. Please note, this is the first time the Withdrawal Agreement has been tested by parliament and negotiators should expect the need to find further compromise."

He said he shared concern overs of the existence of a 'backstop' - a back up plan as a way of maintaining an open border between Northern Ireland and the Republic of Ireland, because while Northern Ireland would leave the EU with the UK on March 29, the Republic would remain part of Europe.

The backstop would keep the whole of the UK aligned with the EU customs union after the Brexit 'implementation period' ends in December 2020, but only if the two sides have not agreed a new formal trade deal in that time.

However, some fear the UK would continue to follow EU trade rules for an indefinite time without having any say over them because it was no longer a member.

Mr Thomas said: "The backstop ties us to aspects of the EU and stops us implementing any new free trade deals. The Attorney General confirmed to me that, under this agreement, the backstop is inevitable and potentially indefinite.

"The EU can now allow the backstop to go on and on if the government do not compromise in response to EU negotiators' demands. The French have already indicated this could be the case with fishing rights."

However, he said if there would be a guarantee of a legally binding vote on whether the UK entered into the backstop, or the implementation period, he would be "minded to support the deal." This, he said, would have to take place in mid 2020, when there was a greater understanding of how trade negotiations were developing.

Until then, he stressed: "I want to be clear I absolutely, fundamentally oppose the provision of the backstop."

He described the public as "bewildered, confused, puzzled, perplexed, baffled, stumped, mystified, stupefied, nonplussed, muddled and befuddled" over the ongoing activity in parliament surrounding the agreement, and claimed: "Most of which is designed instil fear in people and to frustrate the Brexit process."

The vote in parliament begins this evening at 7pm.