Research carried out by PricewaterhouseCoopers on behalf of the Internet Advertising Bureau (IAB) reveals that advertisers spent £814m on affiliate marketing and lead generation in 2012, with an ROI of £11 for every £1 spent.
The study shows that 3500 advertisers and 10,000 publishers are engaging in online performance marketing (OPM), which the IAB described 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.'
Price-comparison, voucher, loyalty and cashback sites including Comparethemarket.com, Vouchercodes.co.uk, Nectar and Quidco are the best-known examples of OPM.
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.