Ed Miliband has said a future Labour government would introduce “fair” and “sensible” controls on immigration.
The Labour leader said his party had made “mistakes in the past” on the issue and had learned from them.
He announced plans to make it illegal for employers to undercut wages to end “the epidemic of exploitation”.
Earlier, a leaked document suggested Labour wanted its MPs to “move the conversation” away from immigration when campaigning in constituencies.
Speaking in Great Yarmouth, the Labour leader set out plans to stop cheap foreign workers replacing British staff, saying a future Labour government would pass a law to criminalise such behaviour Reported BBC.
He promised a “sensible approach” to immigration controls, not “false promises or false solutions”, adding that he was “serving notice” on firms which exploited workers.
He was speaking as a leaked Labour strategy document. In it, MPs were told not to send out leaflets about immigration to all voters because it could prove to be “unhelpful”.
They were also instructed to “move the conversation on” to other topics if voters expressed concerns about border controls.
The document, entitled Campaigning Against UKIP, says Labour campaigners should listen to the concerns of voters who are leaning towards UKIP.
It claims immigration is the issue “people most often cite” when explaining why they support Nigel Farage’s party, which ran Labour close in October’s Heywood and Middleton by-election in Lancashire and is targeting a number of Labour-held seats in May’s general election.
“Volunteers and activists must understand and acknowledge electors’ concerns about immigration on the doorstep, which will mean hearing opinions that may not gel with their own,” it says.
The document highlights the changes in Labour’s immigration policy since 2010 and says campaigners should “contextualise the problem as something that Labour has a clear plan to improve”.