Marketers are being warned that the much vaunted tweenager group may not be as attractive as once thought when it comes to autonomy and purchasing power.

According to a report by market analysts Datamonitor, the spending power of children between the ages of 10 and 13 is levelling off.

In the past five years tweenagers have had a 65% increase in their income from £600m in 1997 to £1bn last year. However, Datamonitor said that by 2007 their spending power is expected to slump to a quarter of what it was between 1997 and 2002.

Author of the report Piers Berezai said: “Many marketers have been pursuing a ‘get them young’ strategy and had the common view that tweens are growing in influence and have increasing amounts of disposable income.”

But Berezai warned that the growth in numbers of tweenagers in Europe was in decline and that their spending power was levelling off “may force many to rethink their marketing strategies”.