MARK Harper has nailed his colours to the Brexit mast and launched a massive broadside against Prime Minister Theresa May’s Withdrawl Agreement that will see a crunch vote in the House of Commons next Tuesday.

The Forest of Dean Conservative MP, speaking in the Commons on Wednesday during the five-day debate on Brexit, told his party’s leader that he will not be voting for her unless she changes her deal, which seems highly unlikely as Mrs May is sticking to her guns that it is the best possible agreement for the country.

However, Mr Harper did say it was ’not too late’ to think again and warned, if she did not change her mind, he would vote against her and the party ’for the first time in 13 years in Parliament’.

Mr Harper also claimed that, if the deal was voted through next week, it would cause massive rifts with the Democratic Unionist Party in Northern Ireland, who have propped up the Conservatives in the Commons since they lost their overall majority at the 2017 General Election.

Indeed, he said the Conservatives could be ’in office but unable to govern’ unless the Northern Ireland ’backstop’ is taken out of the Agreement.

Mr Harper, a former Government chief whip, told the Commons: “It is not too late for the Prime Minister to think again, to come before the House before the vote on Tuesday and to say that she is going to change the Withdrawal Agreement and deliver that message to our European partners.

“If she does that and the Withdrawal Agreement is changed, I, for one, will happily support the Government, and I believe that the majority of MPs in this House will do so. It will unify our party and bring our DUP allies back with us.

“If she does not, I regret that, for the first time in my 13 years in Parliament, I will be unable to support the leader of my party and the Prime Minister of my country.”

As for the Northern Ireland ’backstop’ issue, Mr Harper added it could lead to a constitutional crisis between the Government and the DUP, leading to years of ’discord’.

He told the Commons: “Because of the importance of Northern Ireland, my colleagues need to reflect on the fact that, if the deal were voted through next week, it is my belief, having listened carefully to what they have said, that the relationship between our Democratic Unionist party allies and the Prime Minister would be fractured beyond repair and what we saw yesterday, when we were defeated three times in this House, will be a state of affairs repeated on a number of occasions day after day after day.

“I think we would be in office but unable to govern our country effectively. Colleagues need to think about that.

“The Irish Government, the British Government and the EU have all said that they do not want to see a hard border or infrastructure—we are all committed to that and we are all supposed to be committed to reaching a deal on a future relationship—so I do not see any need to have the backstop in this deal.

“It is clear to me that, if the backstop remains in the deal, the Prime Minister will not be able to get it through the House.

“If the ?Cabinet’s deal is defeated—this is the Cabinet’s agreement, not just the Prime Minister’s—the Prime Minister should go to the European Council at the end of next week and say that any deal with the backstop will not be passed by this House and that they should think again.

“I think they will reflect on the fact that, if the fifth largest economy in the world and a close defence and security partner is leaving the EU, they have a choice: do we leave with a good, positive relationship on which we can build in the months and years to come, or do we leave with a spirit of rancour and discord?

“That is something our European partners will have to reflect on. I hope that, if they reflect on that, they will reach a wise and sensible decision and we can reach a sensible agreement.”