Monarch Group chief executive Andrew Swaffield and Tui Group chief executive Fritz Joussen have become the latest industry leaders to speak out against a British exit (Brexit) from the European Union as concerns at the prospect sent the pound to a seven-year low against the dollar on Monday.

Swaffield told Travel Weekly: “It will be extremely damaging to UK aviation and the UK travel industry. Aspects of life in the EU are taken for granted. Once we lose them we’ll realise what value they held.”

Joussen said: “I hope the UK leaders can convince the population.”

Six government ministers, including culture secretary John Whittingdale, who is responsible for tourism, lead the campaign for an exit.

Joussen told Travel Weekly: “As a German, I’m not in a position to give advice. As a European, I think it’s odd. If the pound devalues, customers will pay more when they go on vacation. But this is at the edge of my thinking. It’s more important for me as a European, [and] as a company that is listed and headquartered in the UK.”

The bosses of Heathrow, Gatwick and Manchester airports joined Ryanair’s Michael O’Leary and easyJet’s Carolyn McCall in calling for the UK to stay in the EU, as Sir Richard Branson warned leaving would be “very damaging”.

Lawyer Alastair Long of Hill Dickinson warned: “Brexit will create considerable legal uncertainty for the industry.

“Access to the single aviation market would cease, jeopardising the freedom that enabled low-cost carriers to proliferate.

“Brexit also calls into question the UK’s rights under agreements with third countries, for example the EU-US Open Skies Agreement.”

A referendum on Britain’s membership of the EU will be held on June 23.