US treasury secretary Henry Paulson plans to give away nearly all his estimated fortune of $800m (€619m) to charity, following his gift of $100m worth of Goldman Sachs stock to environmental education, according to sources close to his plans.

Paulson, who stepped down from running Goldman Sachs in June after eight years, transferred 637,500 shares in the US investment bank last March to an unnamed recipient. The shares, worth about $100m at the time but now worth $135m, went to the Bobolink Foundation, Paulson's 21-year-old environmental charity, according to sources.