Ed Miliband will today launch an attack on companies which employ most of their staff under controversial zero-hours contracts.
The Labour leader will also "name and shame" high-street giant Sports Direct as part of his speech.
Mr Miliband will call for an end to "Victorian practices (that) have no place in the 21st century".
He will say: "A graphic symbol of what is wrong with the way this country is run is the army of people working on zero-hours contracts with no security while a few people at the top get away with paying zero tax."
He will warn that zero-hours contracts are "becoming the norm" in parts of our economy, with an estimated more than 1.4 million people now employed this way.
It comes two years after it emerged the Church of Scotland had hundreds of staff on zero-hours contracts, while the Royal Mail had 5,000.
Supporters say the contracts give both employers and employees flexibility. But unions warn that they leave staff without guaranteed hours or wages.
Mr Miliband will name Sports Direct, owned by the Rangers' majority shareholder Mike Ashley, as a firm which hands out the deals.
He added: "Sports Direct has thousands of its employers on zero-hours contracts, the vast majority of its workforce.
"Sports Direct has predictable turnover, it is a modern company with stores on many high streets and, judging by its success, where many people shop.
"But for too many of its employees, Sports Direct is a bad place to work."
Labour says that if it forms the next government it will give employees the legal right to a regular contract if they work regular hours. They would also be able to refuse to work outside their contracted hours and receive compensation if shifts are cancelled at short notice.
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