Aon is locked in a £5m legal battle with automotive services group Inchcape.

The dispute relates to Aon's acquisition, from Inchcape, of all the issued shares in Bain Hogg Group. Bain Hogg's business involved the provision of advice on pensions.

According to Aon, Inchcape agreed to indemnify and keep Aon indemnified, as trustee of Bain Hogg, "against 90% of all liabilities [and damages]…arising from or in connection with advice given on the sale of pensions". Under the terms of this agreement, Aon is claiming £5,376,386 "by way of contractual indemnity, alternatively as damages".

Aon said Inchcape had "refused and continues to refuse to pay [the sum]".

An Inchcape spokeswoman said the company was "vigorously refuting the claim".

Aon completed the acquisition of the issued shares in Bain Hogg Group in 1996. Under the terms of the deal Aon became the ultimate parent company of Bain Hogg.