It would also have to accept that the decision, already taken, to move two key EU agencies from London to Paris and Amsterdam would be irreversible, he says.
Duff, now a visiting fellow at the European Policy Centre and President of the Spinelli Group, says the possibility, however remote, of the UK remaining in the EU cannot be ruled out.
Recent excursions by former UK Prime Minister Tony Blair and numerous others from the British establishment “have lit up the argument about whether the UK can, and if so will change its mind about Brexit,” Duff says.
In a new policy paper, ‘Brexit: What if Britain changes its mind?’, Duff explores the new terms and conditions that would be likely to apply to the UK’s renewed membership.
The former Liberal Democrat MEP says these might include reaffirmation of ‘ever closer union’ through the full restoration by the Westminster parliament of the European communities act 1972 and the repeal of all ‘withdrawal’ legislation; guarantees that the decision to revoke Article 50 was sincere, durable and legitimate in domestic terms; agreement to drop mandatory referendums to ratify EU treaty change and agreement to contribute more to a higher EU budget under a reformed financial system, including an end to Thatcher’s rebate.
On the thorny issue of citizens’ rights Duff says that a formal endorsement of the European Charter of Fundamental Rights would be required “by ditching any pretence to a British opt-out.”
He also says that in the field of justice and home affairs, the British opt-outs in civil and criminal law would have to end for it to be allowed to stay in the EU.
On refugee policy, the UK would have to show a “commitment to a common asylum and immigration policies, including acceptance of its fair share of refugees.”
Duff says that in the financial sector, Britain’s continued membership of the EU would hinge on its “engagement with banking union and commitment to never again seek to block the reform of economic and monetary union governance.”
The UK, he argues in the paper, would also have to agree to participate in permanent, structured cooperation in defence.
The only concession he is prepared to make to eurosceptics is that the UK would not be obliged to join the Schengen area or the euro.