Sir Ivan warns that the remaining 27 EU member states may make huge financial demand if the UK must stay in the single market

Ivan Rogers has said that for the UK to be part of the EU single of about 500 million people, it has stated that Britain would have to pay big cash sum in exchange for the single market.

Speaking further, he stressed that the issue of Britain’s exit bill would be challenging from the beginning of negotiations and anticipated it coming to a head at a “gory” meeting of EU leaders in 2018 autumn.

Sir Ivan also while speaking to MPs on the Brexit select committee, stressed that the other 27 EU nations are going to come up with an amount for the UK to pay for a transitional and free trade deal.

On the other hand, he included that the loss contribution to the European Union would be huge, thus could be used as a bargaining chip by both parties.

He stated that: "I think we can expect a number of them (EU countries) to think - well, if the British want a future trade deal, and they want some form of transitional arrangement before a future trade deal - all big ifs - then this will come together at some gory European Council in the autumn of 2018 and it will come together with the money equation.

"There will be some who will want to play hardball and say, 'well, absent British money over a transitional period, why the hell should we give them any trade deal?'"

Sir Ivan, who resigned last month, sparking controversy, repeated his claim that it would take until the mid-2020s before there was a full divorce agreement and free trade deal with the EU.

He said the UK needed to try to negotiate the "biggest free trade agreement ever struck" that should be "unprecedentedly good and bespoke".

Sir Ivan added that falling back on no deal and World Trade Organisation rules would leave the UK in a "legal void" which would cause "massive damage from day one".

Sir Ivan never ended his speech without sounding a note of warning to the UK not to go into any form of trade deal without including financial services on such agreement. Because if that happens, the UK will be on the losing end, as the country export more financial services than goods.