TIME is running out for the UK Government to come up with a viable post-Brexit customs plan, leaders of some of Europe’s biggest companies have told Theresa May.

Members of the European Roundtable of Industrialists[ERT] said “clarity and certainty” were now needed and warned that "uncertainty causes less investment".

They spoke out after a private briefing with the Prime Minister in Downing Street when she explained about the work that was underway in Whitehall on the UK Government’s two customs models; the new customs partnership and maximum facilitation or “max-fac”, both of which Brussels has dismissed as unworkable.

Mrs May underlined the importance of ensuring that Britain’s future trading arrangements with the EU were as frictionless as possible, delivering on the commitments to avoid a hard border between Northern Ireland and Ireland, and allowing the UK to pursue an independent trade policy.

Downing Street said: “The PM recognised the necessity of providing certainty for businesses, pointing to the agreement of an implementation period at the European Council in March to provide time to allow businesses to prepare for the new arrangements.”

David Davis, the Brexit Secretary, gave the business leaders an update on progress in the negotiations.

In the next fortnight, Mrs May is expected to publish a Brexit White Paper, setting out her priorities for Britain’s future relationship with the European Union ahead of the key European Council on June 28/29.

It will be a bid to get on the political front foot in the negotiations with the Conservative Government presenting for the first time a “detailed, ambitious and precise” explanation of what it hopes the final deal will deliver for the UK.

No 10 said those present at the Downing St roundtable meeting discussed regulatory standards with Mrs May and Mr Davis reiterating the UK’s commitment to maintain high ones. There was consensus, it added, that reaching a robust agreement on data-sharing was vital to the country’s future economic and security relationship with the EU.

After the meeting, the ERT put out a statement, saying: “We appreciate the Prime Minister's openness to ERT views and were able to express our own views and concerns.

"The uninterrupted flow of goods is essential to both the EU and UK economies. This must be frictionless as with a customs union. We need clarity and certainty because time is running out. Uncertainty causes less investment," it added.

Among the business leaders at the meeting were: Harald Kruger, the Chief Executive of BMW; Moya Greene, the boss at Royal Mail; Vittorio Colao of Vodafone and Carl-Henric Svanberg, the outgoing Chairman of BP.

Liberal Democrat MP Tom Brake, a leading supporter of the pro-EU Open Britain campaign, said: “Theresa May is traipsing round any round table she can find and asking what she should do with her plans for a ‘customs partnership’ and is being repeatedly told that she needs to chuck it in the bin.

“Without a customs union with the EU, Britain’s exporters will be in serious trouble. The time for political games is over, we need to get serious about protecting jobs and supply chains from the havoc that either a ‘customs partnership’ or ‘max fac’ would bring.

“Pressing ahead with either scheme would be to put ideology before about what is right for the country and no government would be forgiven once the inevitable jobs cuts start to bite,” he added.