The traditionally conservative employers group also released an opinion poll showing three-quarters of its members supported action to counter climate change with strong backing for solar, wind, and even tidal power.

Only 9% of the 1,000 bosses “strongly agreed” that the proposed new reactors at Hinkley Point C would make Britain more economically competitive.

Less than a fifth strongly believed Hinkley would make the UK more strategically secure although a different poll taken 12 months ago showed a huge majority in general favour of new nuclear power stations being constructed.

“The IoD backs nuclear as a reliable source of low-carbon energy, but each project has to make economic sense. Hinkley Point C would generate reliable power for 5m homes, but given the costs, the government is right to take one final look before signing off,” said Dan Lewis, senior infrastructure policy adviser at the IoD.

However, Lewis attacked ministers of all parties for focusing on reducing carbon emissions but underplaying the other two “crucial aims of energy policy”, delivering secure and affordable power.

“Government policy at the moment is creating all sorts of bizarre outcomes. Instead of accelerating moves to safely frack for gas and oil in the UK, we are importing coal and oil from Russia, and gas and oil from Norway, with the extra costs and emissions that involves.

“Instead of building cleaner gas plants to meet demand when renewables can’t, the government has been subsidising more polluting diesel-fired plants,” he added.

The IoD survey shows members are split over shale exploration with only 53% strongly or somewhat in favour with nearly 30% strongly or somewhat opposed.

Around 14% of those surveyed neither supported nor opposed fracking, while a very high 53% strongly supported solar arrays, with 45% similarly in favour of offshore wind and 57% behind wave and tidal, neither of which have been tested at scale in Britain.

Hinkley has been put under new scrutiny following the EU referendum and decision by David Cameron to quit as prime minister. A final decision by new business and energy secretary, Greg Clark, is expected next month.

EDF, the French promoter of the scheme, took a final investment decision to proceed with the Somerset project after a raft of delays but Hinkley’s many critics believe the scheme is too expensive.

A previous government agreed to pay EDF a guaranteed price of £92.50 per megawatt hour for the 35-year duration of the scheme, even though the current cost of wholesale electricity is half that figure.”