The EIAA was formed last year by heavyweight pan-European digital media owners.
The report, conducted for the EIAA by the market research company NFO Infratest, tracked the effect of combining online advertising with TV, radio and print in 15 brand campaigns across the UK, France and Germany.
Results showed that in the UK, the addition of online advertising to television and print campaigns almost doubled the audience reach, from 35 per cent to 64 per cent.
In terms of brand recall, TV alone resulted in a 26 per cent increase in recall, while online and TV used together resulted in a 48 per cent recall rate.
The report also found that online advertising was highly effective with targeted radio and print campaigns, such as for the youth market.
The 15 campaigns used covered seven categories: mobile phones, finance, health and beauty, FMCG, telecoms, automotive and business to business.