Christian Aid is urging leaders of the Big Four accounting firms to come out in favor of country-by-country tax disclosure for multinationals.

The non-governmental organization believes that tax avoidance by multinational companies costs developing countries some $160 billion a year in lost revenue.

According to the Tax Research blog, Christian Aid is urging its 80,000 members to join in a mail-in campaign targeting the heads of the Big Four: John Griffith-Jones (KPMG), John Connolly (Deloitte), Jim S Turley ( Ernst & Young) and Ian Powell (PriceWaterhouse Coopers LLP).