However, the group reported an overall revenue growth of 1.4 per cent.
Alain de Pouzilhac, the Havas chairman, said the performance had "reinforced our confidence in achieving our objectives for 2005".
Despite the 3.3 per cent drop in UK revenue, Havas insisted the group was on course to achieve positive growth in the UK for the full year, thanks in part to synergies resulting from the development of its "power of one" integrated strategy.
The dip in the group's UK revenues was offset by the £135 million Radio Shack account win by its Arnold Worldwide subsidiary in the US and the global Diesel account awarded to ER27. Havas agencies delivered a net rise in new business of 45 per cent compared with the first quarter of 2004.
Problems in Australia were largely responsible for a 2.7 per cent drop in revenue in the Asia-Pacific area. However, France and the rest of Europe saw growth of 2.2 per cent and 2.1 per cent respectively, while revenues from Latin America grew 19.7 per cent.
Meanwhile, Havas continues to oppose a call by the corporate raider Vincent Bollore, who owns 20 per cent of the group, for four seats on the board.