Potential investors in the Sizewell C nuclear plant should have significant experience in producing big infrastructure projects and will be required to pass strict national security checks.

Ministers yesterday formally began a process to attract billions of pounds of private investment for the proposed power station in Suffolk, which could generate enough electricity to supply six million homes. Estimates suggest the plant could cost up to £30 billion.

The government co-owns the Sizewell development vehicle with EDF, the French energy group leading the project, after ministers bought out CGN, the Chinese state nuclear group, last year amid security concerns.

The government has put more than £1.2 billion of taxpayers’ cash into developing the plant but the state and EDF want to retain stakes of about 20 per cent in the construction phase. They have been working with bankers from Barclays and Rothschild to sound out potential backers for at least a year but are now seeking applications for a formal investment process.

Nuclear projects have long struggled to attract private investment because of the huge up-front construction costs and the industry’s track record of budget overruns and delays.

Ministers have established a “regulated asset base” model offering regulated returns, which is designed to make the investment more appealing.

However, prospective investors have been told they must meet a set of criteria before they can take a stake, constraining the would-be pool of backers. Investors must also “bring sufficient benefits to the company to justify their involvement” and “add value to the project”. The government added: “Investment is being sought from those with significant experience in the delivery of major infrastructure projects, especially in large-scale nuclear or other complex energy or infrastructure projects. Drawing from this experience would ensure Sizewell C benefits from expertise in areas such as project risk management, cost control, and instilling projects with a culture of commercial focus.”

•The Court of Appeal has granted campaigners from Together Against Sizewell C permission to appeal against the High Court’s refusal to allow a judicial review of planning consent for the project. A spokesman for Sizewell C said the claims had been dismissed.