High street chain Sports Direct has dismissed an attack on its employment practices from Ed Miliband.
The Labour leader accused the retail giant of being a "terrible" employer with "Victorian practices" because the vast majority of its workforce is on zero-hours contracts.
But a spokesman for the firm brushed off the criticism, telling the BBC: "With enemies like these, who needs friends?"
Mr Miliband singled out Sports Direct as he launched his latest assault on the use of zero-hours contracts, which give employees no guarantee of paid work.
In the 20-minute speech at the University of Warwick, Mr Miliband also said big changes were required to make Britain a more equal society.
Claiming that 17,000 of Sports Direct's 20,000-strong workforce are on zero-hours contracts, Mr Miliband said of the firm: "It has predictable turnover, it has big profits but, for too many of its employees, Sports Direct is a terrible place to work.
"We cannot go on with an economy that allows businesses to use zero-hours contracts as the standard way of employing people month after month, year after year."
He added: "These Victorian practices - the epidemic of zero-hours contracts that we see at Sports Direct - have no place in the 21st century.
"We are going to change what I call the zero-zero economy - of zero-hours contracts, and zero tax for those at the top.
"We've listened to businesses and we've listened to workers.
"Under Labour, if you work regular hours you will have a legal right to a regular contract.
"This country is too unequal and we need to change it. The Tories won't do anything about low pay because they think that's how Britain competes in the world."
Sports Direct agreed last month to make major changes for staff on zero-hours contracts after legal action brought by a former employee.
Job adverts will be rewritten and employment contracts for future zero-hours staff will make it clear that work is not guaranteed, said Leigh Day, the law firm which represented Zahera Gabriel-Abraham in an employment tribunal claim for sex discrimination, unfair treatment and breach of holiday rights.
A spokesman for the firm said: "The company will continue the process of reviewing, updating and improving our core employment documents and procedures across our entire business beyond its existing compliant framework."
Business and Enterprise Minister Matthew Hancock said Mr Miliband was not announcing any new policies to tackle zero-hours abuse and insisted that the Government was already taking action.
He said: "Another rehashed policy from Ed Miliband can't hide the fact that he still hasn't got an economic plan to secure a better future for Britain. He's just not up to the job.
"We're already tackling the abuse of zero-hours contracts - after 13 years of Labour doing absolutely nothing about it. And Labour authorities continue to use them - even Ed Miliband's own Doncaster Council have admitted using 300 people on zero-hours contracts.
"All Labour offers is more spending, more borrowing and more taxes, which would make people on low pay worse off."