Ministers have been requested to face the Commons over the Prime Minister's surprise announcement on energy bills.
Commons Speaker John Bercow has granted shadow energy secretary Caroline Flint an urgent question on the plans, which Labour said are "unravelling by the minute".
David Cameron announced during Prime Minister's Questions on Wednesday that energy companies would be required in law to give customers the cheapest available deal.
However, there was little detail about how such a scheme would work and the Department for Energy and Climate Change appeared to have been taken by surprise by the announcement.
"This is a policy unravelling by the minute," a Labour source said.
A spokesman for the Department for Energy and Climate Change was unable to say who would be answering the urgent question for the Government.
Energy Secretary Ed Davey was this morning giving a speech on energy market reform in the City.
The Press Association, photo by Mukumbura