Miliband fired up the troops at the annual party conference Tuesday by denouncing "the fast-buck culture of the past 30 years." His speech won applause from delegates in Liverpool, The Independent reported.
Business leaders were less enthusiastic.
Lord Digby Jones, Brown's trade minister, called the speech a "kick in the teeth for the only sector that generates wealth, that pays the tax and creates the jobs this country needs."
In media interviews Wednesday, Miliband insisted he is not anti-business but wants to encourage "responsibility."
A star of the conference, Rory Weal, 16, received a standing ovation Monday when he attacked the Conservative-Liberal Democratic government's cuts. He said the Labor Party must "create a vision of what a better Britain looks like."
"I owe my entire well-being and that of my family to the welfare state. That is why I joined the Labor party," he said. "That very same welfare state is being ruthlessly ripped apart by a vicious, right-wing Tory-led government."