PricewaterhouseCoopers has tightened its grip on FTSE 100 audits in the wake of Alliance Boots’ departure from the blue chip index.

The Big Four giant is now set to have 41 top flight audits after the move, which saw British Energy moving up from the FTSE 250. The firm has now gained two top flight audits this month.

The other firms are now almost level pegging in terms of audit clients, but lag far behind PwC. KPMG will now have 21 clients while Ernst& Young and Deloitte provide audit services to 19 corporates.

Boots’ sale to private equity group KKR and Alliance Boots’ deputy chairman Stefano Pessina has seen it drop out of the top index.

Regulatory watchdogs played down concerns this week that the gap between PwC and the chasing firms could expand into a chasm, stating that the changes were a natural side effect of regular reshuffles. PwC has benefited most from recent shake-ups and other market movements while KPMG has suffered.

Barratt Homes recently dumped Bradford & Bingley out of the index, depriving KPMG of a client and giving PwC another one.