The pledge came as Labour leader Ed Miliband promised to cut overall immigration and force companies to take on an extra apprentice for every non-EU migrant they hire.
Business leaders reacted coolly to the latter announcement, warning it was unworkable.
The Conservatives also weighed in, claiming the measure was potentially "illegal".
The focus on immigration, as the party's annual conference in Brighton got under way, follows allegations Labour has failed to understand the concerns of ordinary people about the issue.
Mr Miliband announced what aides described as a "new approach" on immigration.
Among other measures a future Labour government would introduce would be a ban on employment agencies which use only foreign workers.
It would also raise the maximum penalty for not paying the minimum wage from £5000 to £50,000, and maintain a cap on non-skilled workers.
Forcing companies to train more apprentices will "tackle our standards of living issues that so many families are facing in this country", Mr Miliband said.
Labour believe the move could create an extra 25,000 new apprenticeships over the next five years.
The Conservatives said Labour's ideas were a "shambles" and claimed the plans would be illegal, adding that companies could not exclusively offer apprenticeships to British workers.
Labour hit back, accusing their opponents of "risible" tactics.
It insisted it would not limit apprenticeships to British workers, but said that it expects that they would take up the vast majority of jobs.
But business leaders attacked the proposal. British Chambers of Commerce director general John Longworth described it as "an 'apprentice tax' on employers and job creation".
"Businesses need to be able to choose the talents and resources they need, and sometimes cannot find in the UK," Mr Longworth said.
"This immigration benefits Britain.Penalising good companies by making the grant of a work permit conditional on taking on a UK apprentice just raises business costs and new red tape."
The Institute of Directors said the proposal was "completely removed from reality".
The Confederation of British Industry described as "unworkable" a separate proposal which was floated by Mr Miliband.
This suggested varying minimum wage rates in different sectors of the economy.
Simon Walker, director general of the Institute of Directors, said: "Several of Labour's proposals are completely removed from reality and betray the fact that their authors can have had no experience of running a business. Compelling companies to take on an apprentice for every non-EU employee is a daft policy, which would damage many small and medium-sized businesses just as they are starting to grow."
Transitional arrangements between the UK and Bulgaria and Romania are due to come to an end at the end of this year.
This will mean workers from those countries will have the right to come to Britain to work.