The Government has shut down 19 companies in the last 15 months for scamming £24 million from investors by selling them virtually worthless carbon credits.

The Insolvency Service said the companies had “ripped off” more than 1,500 investors, most of them elderly. The now defunct firms flogged victims Certified Emission Reduction Units (CERs) using high-pressure sales techniques.

Investors were promised massive returns for selling the carbon credits on to companies such as Marks & Spencer and British Airways but most found they couldn’t sell them at all. Companies buying CERs deal in high volumes, meaning there was no market for the relatively modest number they held.

One company alone – Eco Global Ltd – conned £8 million from 230 people over the course of two years. At least 50 of those targeted were over the age of 70.

Victims were told they could expect returns of up to 42% – a number taken from an out of date news article published in 2010. The firm made the majority of its money (£5 million) selling ‘pre-issue’ carbon credits that didn’t exist and wouldn’t be issued until 2015.

Consumer Minister Jo Swinson 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.

“In the last 15 months we have wound up 19 companies for trading in these non-viable credits and we will continue to take robust action against any more companies attempting this scam.”