If the UK is punished by Brussels by being barred from those trade deals, the countries are threatening legal action for breach of contract, according to sources in Brussels.
"When they signed trade deals with the EU, they understood it would include Britain. For some the UK market was a major attraction so to be told they may be excluded in the future hasn't gone down well. Some have consulted their legal departments and might consider taking action against the EU," a source told the British Sun newspaper.
UK Prime Minister Theresa May has said she would trigger Article 50 of the Treaty of Lisbon — the process for starting negotiations on Britain's exit from the EU and its new relationship with the union — by the end of March 2017.
In the meantime, there have been growing calls for Britain not to be allowed the same access to the EU single market, in order to discourage other countries from following Britain out of the EU and pursuing a pick-and-mix membership.
The former Prime Minister of Belgium, Guy Verhofstadt — who now leads the Liberal Democrat bloc in the European Parliament and is the lead rapporteur for Brexit for MEPs — is against the UK remaining in the single market for less money than it is paying now.
"A deal with these conditions would be unthinkable. It would allow the UK to expand its already very favorable position: keeping the best parts and ridding itself of the obligations that come with it. EU Governments would be mad to agree to such a deal and I can tell you: the European Parliament will never agree to a deal that ‘de facto' ends the free movement of people for a decade, while giving away an extra rebate in exchange for all the advantages of the internal market.
"What would stop other countries from asking the same exceptional status? Do we really want euroskeptics elsewhere in Europe to invoke the British example of 'having their cake and eating it'? Everyone can see that this position is irresponsible because it's not sustainable in the long run."
My reaction to Amber Rudd going against UK values: https://t.co/XrAwLmLtQ1— Guy Verhofstadt (@GuyVerhofstadt) October 6, 2016
The EU will defend the rights of her citizens wherever they are
"The only new relationship between Britain and the European Union can be one in which the UK has an associated status with [fewer] obligations but equally less rights. And if this is not feasible, the fallback position will be an ordinary trade agreement between Britain and the EU."
If non-EU countries that have struck trade deals with the EU — which are contingent of the UK being part of those deals — threaten to take legal action against Brussels for breach of contract, the whole matter of Brexit could drag on for years.