German business confidence has slid more than expected in July as worries about the impact of the euro zone debt crisis deepen.

The Ifo institute said its confidence index dropped to 103.3 points in July from 105.2 in June. It was the third consecutive month-on-month fall.

Germany so far has been relatively unaffected by the debt-related economic troubles in the 17-nation euro zone but worries are growing that it won't be able to escape the fallout.

Wednesday's Ifo reading was the lowest since the index stood at 102.0 in March 2010.