The drop was in sterling terms, though Experian reports in US dollars. The weaker pound meant that dollar revenues for the division dropped from $328m in 2008 to $274m for the 2008 financial year.
Summing up the performance of the division, Experian said new media activities had produced growth, but traditional activity had been further affected by the downturn in the financial services market.
There was double-digit growth in online contact data management, email service and online competitive intelligence. In addition, Experian's Mosaic segmentation tool was taken up by more public sector clients.
The interactive division, which includes the consumer-facing credit checking business CreditExpert, grew sterling revenues by 47%.
Experian's overall UK and Ireland profits (before interest and taxes), which include the credit services and decision analytics divisions, grew 8% in sterling terms, but shrank 8% in dollar terms to $213m.
The global picture was better, with post-tax profits up 13% to $494m and revenues up 8% to $3.87bn.
Don Robert, chief executive of Experian, said of the outlook: "While we expect little organic revenue growth in the first half, for the year as a whole our objective is again to broadly maintain margins, grow profits at constant currency and deliver strong cash flow conversion."