The boss of FTSE100 firm GKN has has warned an exit from the European Union would be “deeply harmful” – and says the issue is already affecting inward investment.

Nigel Stein, chief executive of the Midland engineering giant, said the UK would be at risk of losing investment if it lost its position of influence in European policymaking.

The firm is a global market leader in the design and manufacture of aircraft assemblies, components and advanced electrical systems, and employs hundreds of people across the region.

Mr Stein said: “From a GKN perspective the prospect of the UK talking itself into an exit from the EU would be deeply harmful to our industries, where we are part of a European footprint, not a country in isolation.

“Competition for investment is intense. And if there is one thing investors hate, it’s uncertainty. Be sure, even now the uncertainty over the UK’s position in Europe is being used against us.”

GKN supplies specialised parts to the car and aerospace industries across the world.

Redditch-headquartered GKN employs more than 700 people at its Driveline operation in Erdington, making propshafts and sideshafts for 1.7 million vehicles a year.

Another 150 jobs are at GKN Wheels in Telford, while the firm also has sites at Leek in Staffordshire and Minworth in Birmingham.

West Midlands region MEP Phil Bennion, Lib Dem employment spokesman in the European Parliament, commented: “This view by GKN is concerning but not unexpected given the global nature of their business. The list of companies now warning against the danger of an EU exit is growing daily.

“This is just another example of how rightwing Tories and UKIP are putting billions of pounds of investment and millions of jobs at risk by undermining our membership of the EU and the single market.

“Jobs here in Shropshire, Worcestershire and Birmingham depend directly on our trading relationship with other countries in the EU single market. It is a club which we need to stay as full members.

“If UKIP and rightwing Tories get their way and pull us out of the EU, it would be a massive blow to UK manufacturers.”