Airbus has told MPs that Britain risks losing the “crown jewels” of its aviation industry to China as a result of Brexit, putting up to 7,000 wing-manufacturing jobs in Wales at risk.

The company’s senior corporate representative in the UK warned the business select committee that the threat of new customs bureaucracy and reduced employee mobility could deter long-term investment and accelerate a shift to Asia.

Though there are no current plans to move, Katherine Bennett said, she was “fighting to ensure that wing design – the crown jewels of aerospace – remains in this country”.

“I need to let you know, committee, that other countries would dearly love to design and build wings,” she told MPs. “Some of them already do; we do build wings in China now, and believe you me they are knocking at the door as a result of the situation we are in in this country.

“Every single thing we export goes into the EU – we don’t export anywhere else – so non-tariff barriers are a really big thing for us,” added Bennet. “[This is] yet another burden going on my shoulder when I am putting a good case for the UK”.

The hearing followed written evidence on Monday which saw experts predict new customs obstacles would add £1.5bn a year to the industry’s costs.

The Airbus facility at Broughton, North Wales, was the birthplace of such aviation classics as De Havilland’s Comet and Mosquito planes, but now builds up to 60 wings a month for its European parent company.

The wings are transported for final assembly in Toulouse, France, in specialised Beluga cargo aircraft that have just a two-hour turnaround between flights, something the company says could be impossible if there is excessive new customs bureaucracy.

“The big issue for us on customs is non-tariff barriers [affecting the] movement of parts across the Channel, of which we have a huge number every single day,” she added. “With several [Beluga] movements a day. we really don’t need any customs burdens or paperwork getting in the way.”

The company, which has established an international working group to handle the impact of Brexit, is also worried about its continued access to key workers once free movement ends. About 600 of the group’s 15,000 UK employees are other EU nationals, while 1,300 of the company’s British employees work on the continent.

“In order to get on in our company you have to have worked in another country,” said Bennett. “The most important thing is our sites remain competitive and productive … and I have to say Brexit puts an extra burden on us.”

Other witnesses warned that the British space sector was already losing orders as a result of the Brexit referendum, but that there was little chance of new trade deals making a meaningful difference to its export potential.

Simon Henley, president-elect of the Royal Aeronautical Society, said some UK space companies have already been excluded from even bidding for work.

“Everyone is in a holding pattern at the moment,” said Paul Everitt, chief executive of the industry trade body, ADS. “There is nothing we can’t access today that will change tomorrow [as a result of new trade deals],” he added.

Airbus said it had been speaking to government “several times a week” to warn it of the dangers and was “laying out issues to the nth degree to every part of government”.

But the Department of Exiting the EU has so far refused to publish 58 sectoral analysis reports produced by civil servants into the issues raised by Brexit for different parts of the economy.

On Tuesday, campaigners threatened to take ministers to court if they continued to obstruct efforts in parliament to force disclosure.

Lawyers representing Molly Scott Cato MEP and Jolyon Maugham, of campaign group the Good Law Project, wrote to David Davis and Philip Hammond giving them 14 days to release in full government studies into the economic impacts of Brexit. If they refuse to make the documents publicly available, they said they will start judicial review proceedings in the high court.

“The government’s desperate desire to hide the reality of Brexit from its own people will not work,” said Maugham. “Our old-fashioned, homegrown common law gives us the right to see these documents – not just whatever’s left after a minister, desperate for secrecy, has gone at them with a thick black marker pen.”