Bank of America played a role in Merrill Lynch’s controversial decision to pay $4bn in bonuses in December just as mounting losses were threatening to derail BofA’s takeover of the Wall Street firm, according to people close to the situation.

BofA has said that the payment of $4bn in compensation in a fourth quarter in which Merrill racked up $15bn in losses was sanctioned by John Thain, Merrill’s chief executive.