Over £800 million was spent on affiliate marketing in the UK last year according to an inaugural report by the Internet Advertising Bureau.

The report, undertaken by Price Waterhouse Cooper for the Internet Advertising Bureau (IAB), is the first ever study conducted on the UK Online Performance Marketing industry. The report found that 3500 advertisers and 10,000 publishers used online performance marketing (OPM) throughout 2012 and experienced a return-on-investment of £11 for every £1 spent. In total, £814 million was spent last year, generating sales in total worth £9 billion.

Described by the IAB as digital marketing's "best kept secret", IAB director of research and strategy Tim Elkington said: "Each year [OPM] drives more than two online purchases for every UK adult and causes the equivalent of every UK person to fill out a form showing interest in a product."

According to Marketing Magazine:
The financial sector is the biggest spender on OPM, with a 45% share of the market last year, compared with retailers' 20% share; telecoms and media companies account for 10% of the market.