But as Britain's politics become more polarised because of Brexit, many business leaders are feeling alienated by a party that is pushing through policies on trade and immigration that they say will damage their companies. "Particularly in the case of manufacturing sectors, which in Wales are so important in providing high-paid, high-skilled jobs".
The letter from the groups follows warnings from aerospace giant Airbus SE and vehicle maker BMW AG that time is short before they need to implement contingency plans.
Foreign Minister Boris Johnson says the British people "don't want some sort of hopeless compromise" in the Brexit deal. Brexit done badly will leave us in a worse position than we were before.
International Trade Secretary Liam Fox told the BBC that the European Union needed to understand that Britain was willing to walk away from talks without agreement if necessary, because "no deal would be better than a bad deal".
They expressed concern that a 21-month transition period to give business time to prepare for Brexit is losing its value because little is known about the conditions after exiting.
In his interview in the Sun, Mr Johnson said people "just want us to get on with it".
The second anniversary of Britain's landmark referendum was also marked elsewhere in Europe, with the organizers of one pro-EU march in Berlin claiming to have attracted 1,000 participants.
The European group, which directly employs almost 15,000 people in Britain, warned that crashing out of the bloc would be "catastrophic" and force it to consider its investments.
Airbus Commercial Aircraft chief operating officer Tom Williams said any Brexit scenario had "severe negative consequences" for the United Kingdom aerospace industry, Airbus in particular.
Dr Fox told the BBC it is "essential" the European Union "understands... and believes" the Prime Minister's assertion that no deal would be better than a bad deal.
Crowds waving flags and placards filled Parliament Square yesterday chanting "We demand a people's vote".
While the deal should help maintain the status quo for City banks, it has yet to be formally adopted because it will form part of the wider Brexit divorce settlement.
Under a blue sky, marchers set off from Pall Mall before passing May's Downing Street office - to the sound of boos - on their way to Westminster to listen to speeches by anti-Brexit MPs including Liberal Democrat leader Vince Cable and Tory rebel Anna Soubry.
Britain is on course to end its membership of the European Union next March, having first joined in 1973, but trading will continue for a limited period after that under a transitional period arrangement between the two sides.
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