Some of London’s leading law firms are embroiled in a spat over the latest round of M&A rankings, with Clifford Chance’s (CC’s) City rivals claiming the firm’s performance in Mergermarket’s H1 European deal tables was unfairly exaggerated.

Two major City rivals are believed to have complained about CC’s inclusion of a deal that saw it act for financial advisers JP Morgan and UBS on the £1.2bn acquisition of Chubb by United Technologies Corporation (UTC).