Nineteen financial firms that conned more than 1,500 people out of £24 million through carbon credit scams "preyed on older people", the industry regulator said.
The companies offered "worthless" carbon credits - or Certified Emission Reductions (CERs) - and used high-pressure sales techniques on customers mostly ranging between 50 and 85-years-old, according to the Insolvency Service.
Those firms have been wound up by the service in the last 15 months, Consumer Minister Jo Swinson announced.
She said: "This is a particularly contemptible scam as it not only preyed on older people trying to maximise their savings, but also targeted their sincere desire to make ethical investments. Instead, investors have been left out of pocket with shares that are either worthless or do not exist.
Ms Swinson added that "robust action" would be taken against any more companies attempting the scam.