Mr Paterson and Mr Longsworth will issue the stark warning to German business leaders on Saturday.
Former cabinet minister Owen Paterson and John Longworth, co-chair of “clean Brexit” campaign group Leave Means Leave, will warn a Berlin business leaders that their economy will suffer the consequences if it relies on “cack-handed” Brussels bureaucrats to safeguard Germany’s future.
They will highlight Britain’s position as a top three export market for Germany, adding that a fifth of all cars it produces are sold in the UK, providing jobs for one million Germans.
The conference will be attended by figures including German industry federation chief Markus Kerber and those attending will be urged to pressure politicians into granting Britain a free trade deal with the EU.
Mr Paterson will say: “Germany and the UK have a mutual, strategic and selfish interest in maintaining reciprocal free trade.
“When the UK leaves the EU, it will also leave the internal market of the EU, but will continue to sell enthusiastically from outside.
Mr Longworth will say that a good deal is more important than the "bitter politics" of the EU.
“It is vital that businesses in key member states such as Germany are listened to carefully during the negotiations.”
He will add: “Already, senior figures in Bavaria have warned that they do not want to see a recession in successful exporting parts of Germany caused by cack-handed negotiations in Brussels.”
Mr Longworth will tell the conference that the “voice of business” must drown out the EU’s “bitter politics” in Brexit negotiations.
Mr Paterson will remind Germany of its mutual interests with Britain for the best trade deal.
He will say: ”Make no mistake – no deal is better than a bad deal with the EU, Britain will walk away from the table and revert back to WTO (World Trade Organisation) rules with ease.
"The British Government could compensate business for any EU tariffs by committing less than half of the British net contribution to the EU and, as the best place in Europe to do business, will attract trading partners and investment.
"Starving the EU of access to the expertise and deep and wide capital markets of the City of London will impede EU growth, and we all want the EU countries to be economically strong and grow.
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"We want a system whereby free trade will continue, but in order for this to happen, you need to make representations to your Government and the EU.
"The voice of business must drown out that of the bitter politics of the EU project."
This comes after German finance minister Wolfgang Schauble told the World Economic Forum in Davos, Switzerland that Germany would do everything it could to ensure a successful outcome to Brexit negotiations within the two-year dealing set down in EU treaties.
He said: "The German government will work in these negotiations always in the direction that we minimise any risk and damage for both of us. That's our position.”