A mistake was made in figures relating to online marketing spending that were released last month, the Internet Advertising Bureau has admitted.

In an email sent to its members seen by Revolution magazine, the body said it had recorded the wrong amount of spending on classified advertising in the report, which was conducted in partnership with PricewaterhouseCoopers.

It had originally stated there was a 10.6 per cent increase in investment in this sector during the first six months of the year, taking the total to £385.06 million. But this amount has now been revised downwards to £335.8 million - a 3.6 per cent decline - after it emerged £49.26 million had been included that should have been attributed to search marketing.

However, the overall figure of £1.75 billion for the period - and the 23.5 per cent of the total advertising sector - remains unchanged, meaning internet marketing still holds a bigger share of the market than its television counterpart. "Following a detailed analysis of the January to June 2009 internet advertising expenditure figures, PricewaterhouseCoopers has updated the totals for online classified and search advertising," the two firms said in a joint statement.