The service was launched by the postal service in April 2009, and in less than a year Brightsource has managed 10m packs through Sustainable Mail and 10.2m through Responsible Mail.

Eddie Sheppard, who heads up Brightsource’s postal management services, said: "These figures demonstrate that Brightsource is pioneering greener direct marketing.

"We’ve now met sustainability criteria on over 20m packs in the last 10 months. To have saved our clients over £100,000, and cut carbon emissions at the same time, is a win-win situation."

The two mail tariffs offer discounts on bulk direct mail that adheres to a range of green criteria, including improved sustainability, waste minimisation and increased recyclability.