An efficacy exclusion clause using the broad causal language 'arising directly or indirectly from or caused by, contributed to by or arising from' the failure of a product to fulfil its intended use or function will exclude cover for liability arising from the supply of a contaminated or wrong product, even where the claim is framed as property damage caused by the product rather than as a failure of the product to perform. The distinction between damage caused by a product and the failure of a product to perform its intended function (from John Wyeth v Cigna) does not apply where the exclusion clause uses broader causal language linking the insured's liability (rather than the property damage) to the product failure.
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