The Irish High Court is being asked to hear a case on whether Britain's exit from the EU could be reversed once it is triggered.

Jolyon Maugham, the lawyer behind the legal challenge, says it will be launched in Dublin by the end of January.

Lawyers for the British government have said once the process is started there is no going back, but some EU leaders disagree.

Amid efforts to seek clarification, a letter before action - the precursor step to proceedings in the High Court - is being issued today.

The legal challenge revolves around Article 50, the formal mechanism for Britain to commence proceedings and negotiations to leave the union.

According to Mr Maugham, the Irish proceedings will seek a referral to the EU's Court of Justice over the question of "whether Article 50, once triggered, can unilaterally be revoked by the British government without requiring consent from all other 27 EU member states".  

He argues that such a legal confirmation would mean that Britain could reject the outcome of negotiations if the deal reached is not acceptable, and therefore remain in the union.

Mr Maugham said: “The United Kingdom must retain sovereignty over the shape of its future relationship with the EU.  If we change our minds we must be able to withdraw the notice without needing the consent of the other 27 Member States.

"I want to establish clarity for British voters and deliver sovereignty to the British Parliament over the question of its future relationship with its biggest trading partner.”