Theresa May threatens US with trade war over Bombardier row

“We have contracts in place with Boeing for new maritime patrol aircraft and for Apache attack helicopters and they will also be bidding for other defence work and this kind of behaviour clearly could jeopardise our future relationship with Boeing.”

His comments were endorsed by Mrs May, who has ordered ministers to “engage intensively” with Boeing, the US administration and others to try to resolve the matter.

The dispute centres on a Boeing complaint that the jets were being dumped in the US at low prices after unfair state subsidies from the UK and Canada had helped Canadian-owned Bombardier win an order for up to 125 aircraft with US airline Delta.

Canada’s province of Quebec took a £740 million stake in the C-series programme. The recommended tariffs will only take effect if the US International Trade Commission rules in Boeing’s favour in a final decision expected next year.