If the United Kingdom ends up voting to leave the European Union, the departure will follow years of difficult negotiations focussed primarily at how to validate the rights of the two million Britons living in the EU, a House of Lords report has warned.
The Lords EU committee said that leaving the EU would necessitate difficult and lengthy negotiations that could take years, adding that determining the rights of UK nationals would be a "complex and daunting" component of the exit negotiations.
"This is complex stuff. You are talking about rights of residence, to health care and schooling, about maintenance payments and access to children, about research projects and contracts that cross borders" and resolving such issues “would be a daunting task," committee chairman Lord Timothy Boswell said in a statement.
Under Article 50 of the Lisbon Treaty, which outlines the process for withdrawal from the EU, up to two years of negotiations follow the decision by a state to leave.
However, the report warned that the negotiations to establish a new relationship would take longer than two years, but added that it would be in everyone's interest to come to a settlement.
And any negotiations would be made all the more difficult by the need for any deal to be agreed by the European Parliament and the European Council. The report said the European Parliament would be likely to want to protect the rights of EU citizens living in the EU.
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While the committee did not make a recommendation on which way to vote, the report added that trade deal between the EU and non-EU states take between four and nine years on average to negotiate.
"We don't take a view on whether the UK should leave the EU or not," said Boswell.
"But it is clear that if that's what people decide, withdrawal would mean difficult and lengthy negotiations. It's not possible to predict exactly how long it would take, but comparable international trade deals have taken on average between four and nine years."
The report is another blow to the Leave camp after President Barack Obama warned that if the UK leaves the EU, it would go to the "back of the queue" on trade deals.
However, contrary to the report, those campaigning for Brexit have said the UK would be able to forge a new free trade deal with the EU.
Roland Smith, Adam Smith Institute fellow, responded to the report by saying: "The House of Lords claim that Brexit will negatively effect British expats following a vote to Leave is based on the presumption that the UK will leave the EU in a 'complex and daunting' way, attempting to unpick many treaty obligations and partially replace them with a trade deal."
"This is very unlikely to be the case. The Conservative government, the majority of whom have declared for Remain, are not about to cut off from the EU in a lengthy and complex way. Equally the EU is unlikely to offer anything other than the ‘off the shelf’ EEA deal, similar to Norway and Liechtenstein’s, and will make a tailored deal for Britain impossible to discourage other members from leaving.
"The EEA option would have almost no effect on expats, or much else, because Britain’s single market participation and the four freedoms would stay intact at exit."