Ed Miliband is waiting for a "phone call from Unite or divine inspiration through the ether" before deciding whether he backs a referendum on Britain's membership of the European Union, William Hague said.
The Foreign Secretary taunted the Labour leader for not attending the Commons debate in a week when his general election co-ordinator Tom Watson resigned over the party's controversial links with the Unite union.
In a resignation letter Mr Watson praised Mr Miliband for his "Buddha-like qualities".
Mr Hague said: "The leader of the opposition isn't even here, presumably he is sitting somewhere wondering whether his instructions will come in a phone call from Unite or divine inspiration through the ether, because there is no other way in which he is able to decide on this Bill."
Labour leader Ed Miliband has turned on the trade union Unite - his biggest financial backer - whose votes helped him become leader.
Tom Watson has announced his resignation from the shadow cabinet, amid a row about the influence of the union Unite on the Labour party.