Former minister and prominent Leave campaigner Dominic Raab insisted Britain was in a strong position to strike a deal with Brussels after Sir Ivan Rogers told ministers in October that other EU members believe a trade deal may not be hammered out until the early to mid-2020s.
Sir Ivan also said European leaders believe the Brexit deal is likely to be a free trade arrangement rather than continued single market membership.
Tory MP Mr Raab said Sir Ivan was a “scarred” figure, telling BBC Radio Four’s Today programme: “He was the diplomat who persuaded David Cameron to dilute his ambitions for the renegotiation, which was one reason the referendum was lost. So, he has been rather scarred, in fairness, by his own pessimistic advice in the past.
“But, I think it’s reasonable to set out the very worst case scenario for a five to 10-year period to iron out all the details of a trade deal.
“I respect the Foreign Office’s professionalism, but they have always been very pro-EU, and very anti-leaving the EU.
“Let’s not be consumed by Sir Ivan’s gloomy pessimism, let’s get behind the Government, let’s set out the case for a strong, post-Brexit relationship with the EU on trade, security, and other areas.
“My view would be, go in there, try and get the very best deal, there’s precedence all around the world for signing free trade deals in a shorter period of time than Sir Ivan has said.
“But, ultimately, if we have to leave the EU without ironing out all those creases, then I’m open minded about it. I don’t think we want to end up in some kind of indefinite limbo period, but if that’s what it takes to get a win-win, then I’m open minded about it.”
A No 10 spokesman said: “It is wrong to suggest this was advice from our ambassador to the EU. Like all ambassadors, part of his role is to report the views of others.
“We don’t recognise this. The Government is fully confident of negotiating a deal to exit the EU that works in the interest of both the UK and the rest of Europe.”