This was well ahead of 6.2% that was forecast in their previous report in April and reflected strong growth in display advertising as well as a general uplift in confidence about the UK economy.
Regarded as the definitive measure of advertising activity in the UK because it is the only source that uses advertising expenditure gathered from across the entire media landscape, the report also forecast 6.2% growth for the entire year, a positive revision of 0.6pp.
Internet advertising, including mobile, recorded its highest quarterly total on record, rising 12.8% in Q1 to £1.9bn. Mobile spend also grew 50.9% from a year earlier to reach £502m, according to the estimates.
TV spot advertising (+11.5% to £1.2bn), out of home (+9.7% to £229m), radio (+8.2% to £122m) and cinema (+19.6% to £43.6m) saw particularly strong performances over the quarter, but print media continued to decline.
Magazine brands saw adspend dip 3.9% in Q1, including an 8.6% decline for print, although magazine digital spend increased 11.5%.
Regional newsbrands declined 2.3%, driven by a 5.2% fall in print revenues, although their digital revenues increased by 17.6%.
Furthermore, these spending trends are expected to continue throughout the year with internet advertising forecast to deliver 12.6% growth in 2015, including a 43.4% rise in mobile advertising.
TV advertising is forecast to grow 6.9% this year, followed in terms of growth rates by cinema (6.4%), out of home (+6.3%), radio (+4.3%) and direct mail (+1.9%).
Meanwhile, national newsbrand adspend is expected to decline 4.3% in 2015, magazines by 3.3% and regional newsbrands by 3.0%.
Commenting on the report, Advertising Association chief executive Tim Lefroy, said: "Despite uncertainty in Europe and at home prior to the election, these figures come as a welcome boost. Adspend is growing faster here than anywhere in Europe, to the benefit of our digital economy, creative industries and UK plc."
Data sourced from the Advertising Association, Warc