More than 90 percent of companies operating in the British car industry want the UK to stay in the European Union, a survey commissioned by the Society of Motor Manufacturers and Traders showed.

The companies said access to the single market is fundamental to the UK auto sector’s success.

The industry has been one of the most vocal supporters of EU membership since Prime Minister David Cameron promised an in/out referendum by the end of 2017 if his party wins next year’s election.

The survey found that 92 percent of automotive companies believed that staying in the EU would be best for their business, with 70 percent concerned that a withdrawal would damage their medium to long term futures.

Despite the strong support, SMMT said in a statement that members said they did want to see reform of the 28-member bloc, with many regulations seen as too complex and likely to undermine international competitiveness.

“The position of the UK automotive industry is clear — being part of a strong Europe is critical for future success,” SMMT CEO Mike Hawes said in the statement.

“The recent success of the UK automotive sector is due to its global competitiveness; competitiveness that is enhanced by a supportive business environment at home and access to the huge single market,” he said.

The British car industry enjoyed a renaissance in 2013, hitting a six-year production high due to strong domestic demand and exports outside the European Union.

The SMMT survey said the main EU benefits were access to a single market, integrated supply chains, free movement of labor and the ability to influence harmonized technical regulations across the region.

The EU is also seen as an important bargaining force when it comes to agreeing global trade negotiations.