It would be "politically irresponsible" for the European Union to erect barriers to trading with the UK after Brexit, Liam Fox said as he warned such a move would cause economic damage across the continent.

The International Trade Secretary warned it would be a "self-defeating" move for Europe's leaders if they did not agree to the kind of comprehensive free-trade deal sought by Theresa May.

Dr Fox also warned against "seductive" protectionism, likening it to a class A drug that could "make you feel good at first" but was "disastrous" over time.

In his speech at the Conservative spring forum, with Mrs May poised to begin the Brexit process within a fortnight, Dr Fox issued his warning to the Brussels officials and politicians who will decide the terms of any deal.

"Given the challenges facing commercial interests across the globe, we should all consider whether we really want to create barriers where none currently exist," he said.

"So, we must be absolutely clear that any new impediments to trade and investment in Europe would not only be politically irresponsible, but economically dangerous - and not just for Europe but for the wider global economy too.

"We know that when we leave the EU, we will not have an EU commissioner, MEPs or a seat at the European Council. That is a political decision that we have consciously taken following the instruction from the British people at the referendum. It is a political response to a political decision.

"But it would surely be wholly inappropriate if our political decision was to be met with an economic response - in other words, if barriers to trade and investment were introduced across Europe that would damage the economic potential of all European citizens and those well beyond Europe too.

"That would be self-defeating."

The Cabinet minister was a prominent Leave supporter and urged people to be optimistic about the country's future after Brexit.

"It is time for us to ignore the siren voices, the naysayers and the doom-mongers. Instead of talking Britain down, it is time to talk up our opportunities, our skills and our talents.

"Our plan for Britain is not for a nation cowering in the international shadows but confident, strong and optimistic, willing to lead not follow and helping to shape the world around us".

Dr Fox defended globalisation and free trade in his speech and warned against the "rising chorus of protectionism" in the world.

He said: "Protectionism can be seductive but is a dangerous liaison. I have described it as the class A drug of the trading world - it can make you feel good at first but it can prove disastrous in the long term.

"It is economically destructive, preventing us from reallocating global resources effectively. It is also socially regressive because those on lower incomes spend a higher proportion of their money on goods than services so tariffs and barriers will hurt the poor more.

"And we will all pay the price if those denied the opportunity of global prosperity turn their backs on the partnerships and cooperation that underpin global security."