Colchester MP Will Quince has quit his position as ministerial aide over the Government’s EU withdrawal agreement.

It is understood Mr Quince resigned as aide to defence secretary Gavin Williamson because of his disagreement with the backstop clause of the Prime Minister’s Brexit plan – to avoid a hard border with Ireland.

Writing in the Sunday Telegraph, Mr Quince said: “I wanted to support this Withdrawal Agreement, and I still want to support it, but unless the backstop is addressed to include either an end date or a unilateral exit mechanism, I cannot support it and so am resigning from the Government as a Parliamentary Private Secretary.

“I implore the Prime Minister to go back to the European Union and find another way, to make this Withdrawal Agreement something we can all support.”

At the end of last month, after UK and EU officials signed off the draft withdrawal text, Mr Quince said he was seriously concerned that the UK risked being locked into in an indefinite customs union without retaining the ability to give unilateral notice of its intention to leave.

In addition, he said, with the UK unable to unilaterally leave the protocol relating to Northern Ireland, the union would be put at risk.

Mr Quince expressed “deep regret and sadness” in resigning as a parliamentary private secretary.

In a letter to the Prime Minister Theresa May, he offered his gratitude at having been appointed to the role and his enjoyment working with Mr Williamson.

He said the PM had demonstrated steadfast dedication to secure a deal under challenging circumstances.

He did recognise the “huge accomplishments” of the withdrawal agreement but added: “I cannot lend my support to a treaty which, in my view, is capable of creating such a power and leverage imbalance that it would irrevocably weaken the UK’s future negotiating position, and thereby undermine the positive work you have completed to date.”