Energy company Nuon has misled 200,000 clients and hundreds of companies about a green energy contract known as Natuurstroom, the Financieele Dagblad reports on Wednesday.

The company had promised clients who signed up for the green power scheme they would put a cash supplement added to every bill into new sustainable energy projects. However this did not happen, the paper said.

Nuon earlier denied mis-selling but now admits it ‘did not inform clients sufficiently’.

The company is now trying to work out the best way to contact Natuurstroom clients. The contracts were signed between 1996 and 2002. Some 50,000 people still have a Natuurstroom contract, Nos television said.

The FD calculates it would cost Nuon between €70m and €100m to pay back clients the money. Clients paid up to €60 on top of their regular bills for green investments.

Nuon told Nos television the company has invested €558m on green energy over the past 10 years.