The UK “cannot afford” lose access to the European energy market as a result of an exit from the European Union, National Grid CEO Steve Holliday has said.

Speaking to Reuters, Holliday said that connections with Europe’s wider energy infrastructure and market were vital for the UK and that maintaining that link was “unquestionably essential”.

The National Grid is to now investigate the benefits of EU membership for Britain’s UK energy security and is to publish its findings in the coming months, however National Grid is the latest in a number of British companies to speak out in favour of Great Britain remaining part of the EU.

The country’s new Conservative government has promised a public referendum on the country’s EU membership by the end of 2017, sparking serious debate about its impact on UK business.

Holliday was speaking after National Grid reported its full-year financial results for the year ended 31 March 2015, revealing that the company had invested £3.5 billion in grid infrastructure over the course of the year to improve on its reliability, safety and resilience.

National Grid reported an annual profit before tax of £2.87 billion for the year, up 11% on 2014’s figure.