Millions of British expats in Europe could be entitled to sue the UK government for loss of rights, a senior Tory MP has warned.
Alberto Costa said unless Boris Johnson solved the problem, his government could face a wave of litigation claims.
Alberto Costa, who resigned from the government earlier this year over the issue, wrote a letter to Johnson, calling him to enshrine the rights of EU citizens living in the UK into British legislation before October 31. He warned that failure to do so would unfairly penalise British citizens.
No peacetime British government has ever abrogated the rights enjoyed by over a million of its own citizens overnight"
"No peacetime British government has ever abrogated the rights enjoyed by over a million of its own citizens overnight," he wrote. "As a former UK government lawyer I can reasonably foresee an enormous unprecedented amount of litigation raised by British citizens. This would undoubtedly result in a severe challenge to the stability of your government."
If a no deal Brexit is the outcome, each EU member state would be responsible for deciding what rights UK citizens living in its territory would have.
He warned UK citizens could lose their rights to pensions, healthcare and long-term residency.
Last week Costa led an "emergency task force" to Brussels to meet with Michel Barnier, the EU's chief Brexit negotiator, to discuss citizens' rights.
The cross-party group of MPs were warned that the best way to guarantee the rights of five million citizens most affected by Brexit would be through Theresa May's withdrawal agreement.
Barnier also refused to "ring-fence" the guarantees laid out in the failed treaty despite the looming threat of no deal.