The letter describes the referendum result as only advisory because it was based on “misrepresentations of fact and promises that could not be delivered”.
The barristers argue that there must be a free vote in parliament before article 50 of the EU’s Lisbon treaty can be triggered – paving the way for the UK’s withdrawal.
The initiative has been coordinated by prominent barristers in England, Wales, Scotland and Northern Ireland including more than 100 QCs, among them Professor Sir Geoffrey Nice, a former war crimes prosecutor.
The letter states: “The referendum did not set a threshold necessary to leave the EU, commonly adopted in polls of national importance, eg, 60% of those voting or 40% of the electorate. This is presumably because the result was only advisory.
“The outcome of the exit process will affect a generation of people who were not old enough to vote in the referendum. The positions of Scotland, Northern Ireland and Gibraltar require special consideration, since their populations did not vote to leave the EU.
“The parliamentary vote should take place with a greater understanding as to the economic consequences of Brexit, as businesses and investors in the UK start to react to the outcome of the referendum.
“For all of these reasons, it is proposed that the government establishes, as a matter of urgency, a royal commission or an equivalent independent body to receive evidence and report, within a short, fixed timescale, on the benefits, costs and risks of triggering article 50 to the UK as a whole, and to all of its constituent populations. The parliamentary vote should not take place until the commission has reported.”
Aidan O’Neill QC, an expert in constitutional and EU law and one of the signatories, said: “The Brexit referendum has made clear that the UK is not a united nation state, but a divided state of nations. It has given no mandate or guidance as to what our nations’ future relationship might be with Europe, and with each other.
“If the UK is to survive the result of this vote, a consensus needs to be built up about the way forward. Fully informed discussions and deliberations within and between our parliaments is the only proper constitutional way to achieve this. Precipitate or unilateral action by the UK government to trigger article 50 will simply further divide us.”
Philip Kolvin QC, who coordinated this action, added: “Parliament is sovereign and the guardian of our democracy. MPs are elected to exercise their best judgment on the basis of objective evidence, to safeguard the interests of the country and their constituents for this and future generations. At this time of profound constitutional, political and possibly social and economic crisis, we look to them to fulfil the responsibility placed upon them.”
The letter is the latest initiative aimed at persuading Downing Street not to exercise royal prerogative powers and instead allow parliament to make the ultimate decision. At the weekend, the government turned down a multimillion signatory online petition pleading for a second referendum.
A legal challenge to David Cameron’s assertion that he or his successor as prime minister can begin the withdrawal procedure is due to be heard in the high court next week.
The claim is being coordinated by law firm Edwin Coe LLP, which specialises in class actions in the UK. It acted for 50,000 small shareholders in the Railtrack litigation and also in the Northern Rock judicial review.
Confirming the firm’s involvement, David Greene, a senior partner at Edwin Coe, said: “We are very pleased to be joining the bar team led by Dominic Chambers QC on this issue. This is an issue of crucial constitutional importance in the process of withdrawal from the EU.
“It makes perfect sense for this issue to be determined as soon as possible. The determination will clear the way for the right method to be adopted in serving notice under article 50. We will certainly be pressing the court to deal with the matter swiftly.”
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