However, the European Commission must be satisfied that any resulting deal does not amount to a disproportionate and unlawful level of state aid under EU legislation – a process that could take some years.

“The Commission will not want to rush the process because this is the first time state aid approval has been sought for such a nuclear subsidy,” said Keith MacLean, policy and research director at SSE, forecasting that the European Commission was unlikely to arrive at a final decision before 2015 at the latest.

SSE pulled out of a three-way venture with France’s GDF Suez and Spanish group Iberdrola in September 2011, citing escalating costs. Its exit was closely followed by that of German utility firms E.ON and RWE who sold their joint venture Horizon to Japan’s Hitachi in March 2012 after Japan’s Fukushima disaster accelerated Germany’s exit from nuclear power, putting both company’s finances under pressure.

Centrica, whose departure left no British involvement in nuclear new build, also cited cost concerns as its reason for retreat.

It is thought reactor costs have reached around £7bn each, up from less than £4bn in 2008, partly due to stringent new safety requirements rolled out in the wake of the Fukushima disaster in Japan.