RWE npower, one of the big six power suppliers, has warned ministers not to seal a long-term subsidy deal with the nuclear industry behind the backs of consumers and saddle them with "unnecessarily high bills" for the next 40 years.

The warning from Paul Massara, RWE UK's new chief executive, comes as the Guardian can reveal that up to 15 private sector executives with links to the atomic sector have been seconded to government departments or other public sector roles.

"We are very concerned that decisions currently being taken around guaranteed revenue from new nuclear power stations in return for their delivery could force the next three generations of British consumers to pay an unexpected and perhaps unnecessarily high bill for the next 40 years, especially given the track record of delivery of nuclear power stations," said Massara.

"There must be an open and honest conversation about the future direction of energy bills. Customers must be given the best information to be able to make informed decisions, take control of their bills and reduce their energy waste."

RWE, along with another big six supplier, E.ON, recently sold its interest in the Horizon project to build nuclear power plants in Britain at Wylfa in north Wales and Oldbury-on-Severn, Gloucestershire. The German-owned company has spent more than £3bn in the last three years building gas and wind power installations as it prepares to close old coal-fired plants.

Massara said he understood the warning this week about a looming power crunch from Alistair Buchanan, the head of Ofgem, the energy regulator, but said all technologies should be encouraged to ensure the UK's future energy supply is not only clean and secure but also affordable. "We believe UK customers should not be made to write a blank cheque to pay for new power stations," he added.

A Freedom of Information request undertaken by the campaign group, NuclearSpin.org, showed at least 15 people working for the nuclear energy industry or its consultants have been seconded to areas responsible for policy or regulation, some being paid for by the taxpayer.

EDF Energy, which has asked ministers to consider a 40-year subsidy scheme for its proposed UK plants, has seconded two staff to the Office for Nuclear Regulation (ONR) at the Health and Safety Executive. One is interim programme manager for the ONR's programme at the Sellafield plant in Cumbria and is paid for by EDF. The other is a technical assistant on the Decommissioning Fuel and Waste Programme.

Rolls-Royce, which describes itself as "part of the UK's nuclear industry for the past 50 years", is providing the head of new nuclear capabilities and removing barriers at the Department for Energy and Climate Change (DECC). Sophie Macfarlane-Smith is responsible for "enhancing the capability" of the UK's "new nuclear supply chain and skills". Engineering consultant Atkins Ltd is providing a policy adviser for the Department for Business, Innovation and Skills' commercial nuclear policy team and Babcock, which describes itself as "the UK's largest specialist nuclear support services organisation" has seconded two staff to the ONR.

A DECC spokesperson said secondees brought with them knowledge and experience which are vital to helping the department do its job effectively. "DECC ensures that any secondee is bound by the professional Code of Practice relevant to their industry ... There are contractual measures in place to make sure than any employee seconded into DECC is not placed in a position where there could be a conflict of interest."

• This article was amended on 21 February 2013. The original said that a secondee from EDF Energy to the Office for Nuclear Regulation "costs the ONR between £50,000 and £100,000 a year". In fact the full cost of secondments to the ONR is charged to the nuclear industry. The ONR has also asked us to clarify that it has safeguards in place to ensure there is no conflict of interest; no secondee works on matters directly related to their parent organisation.