The World Wildlife Fund's report on 'the conduct and content of corporate lobbying' found that only 51 per cent of companies in Standard & Poor's Global 100 Index provided 'some degree of transparency around lobbying activity'.
None declared how much they paid to professional lobbyists. The WWF estimates that last year Washington lobbyists billed more than £1.7bn, while the value of Europe's industry could be as much as £62m.
But the WWF found UK businesses the most open about their lobbying of government, followed by those in the US and the Netherlands. Japanese and French companies were deemed to be the most secretive.
The WWF praised ABN AMRO, BP, HSBC and Royal Dutch/Shell for their creation of The Corporate Leaders Group on Climate Change.
But the report said such examples of best practice 'were few and far between'.