Firms that have issued warnings over Brexit

Businesses have been cautious about speaking out on Brexit for fear of alienating customers and souring relations with influential Whitehall officials.

Some companies, such as Wetherspoons , have been markedly positive about the process of Britain's withdrawal from the EU.

But aerospace giant Airbus has joined the small number of firms warning about the state of negotiations .

Here are some of the others...

:: BMW (EUREX: BMWE.EX - news)

The German car manufacturer weighed in last year, when its head of purchasing called Brexit a "very uncomfortable scenario".

It was among a group of major European firms last month to warn that "time is running out" in negotiations.

BMW, along with BP, Nestle (Swiss: NESN.VX - news) and Vodafone, told Prime Minister Theresa May a trade deal with the EU must be "frictionless as with a customs union".

:: Deutsche Bank (IOB: 0H7D.IL - news)

Up to 4,000 workers could be moved from London to Frankfurt, a senior executive from Deutsche Bank warned last year.

Its chief regulatory officer said "we really need clarity" and that staff had "real questions", such as: "Where do I register my children for in the next two years at school?"

Another executive, the head of Deutsche's capital market division in Germany, later said they thought "not thousands but rather hundreds" would be relocated from Britain to Germany.

:: Chubb

US insurance giant Chubb announced it would relocate its European headquarters from London if the UK left the customs union.

It has not directly criticised the government, but said it had been "encouraged by the assistance and cooperation provided by the French government as we have considered our post-Brexit options".

:: Rolls-Royce

The car manufacturer's chief executive called last year for "as little change as possible" as he warned against a "hard" Brexit.

It came days after Chancellor Philip Hammond confirmed the UK would pull out of the single market and customs union.

:: Nissan

Japan's second-biggest carmaker may have expanded operations in Sunderland following secret assurances given by ministers, but it teamed up with Toyota and the Japanese ambassador to head to Downing Street for more talks in February.

The diplomat warned afterwards that: "If there is no profitability of continuing operations in the UK - not Japanese only - then no private company can continue operation.

"It is as simple as that. This is all high stakes that all of us, I think, need to keep in mind."