Almost half of the UK's 350 largest companies say pension debts are impeding bids and deals. According to a new survey from consultant Towers Perrin, 165 companies say deficits now represent the major obstacle to successful mergers and acquisitions.

The figure underlines the impact retirement liabilities are having on merger and acquisition activity in the UK, shown by the aborted takeover of retailer WH Smith by private equity group Permira last year.