The Conservatives have accused Business Secretary Lord Mandelson of "empire building", calling for his department to have a cabinet minister in the Commons.
During a debate on the formal creation of Lord Mandelson's post, secretary of state for business, innovation and skills, Lord Hunt of Wirral said the that £9m spent on the establishment of predecessor department DIUS "just two years ago" has been "completely wasted".
He described the new department as "a ghastly throwback" to the 1970s and "corporatism".
"Can so vast a department really be held to account effectively when its only Cabinet minister is here and not in the Commons?" he asked.
Lord Mandelson said he had spoken in the Lords three days in a row which he argued did not "show any lack of accountability to Parliament".
He said the merger was "remarkably inexpensive" and he had been "surprised" how little it was. "It was the modern equivalent of two and six pence," he proclaimed.
Challenged by the Earl of Onslow on why the government had not acted sooner to start the process of building nuclear power stations, Lord Mandelson said: "If you are asking me a direct question I will give you a direct answer.
"I'm not sure all the decisions taken during the last 10 years concerning civil nuclear energy were the right or most timely ones to have been taken," he revealed.
But he continued: "The mistakes of industrial policy did not begin with this government they are, I'm afraid, very much more long-standing than that."