A Home Office spokesperson emphasised that serious punishments, such as prison sentences, would be only for the most serious offences.
The spokesperson said: "Under the plans, new and clear criteria are to be set out so that employers can co-operate with the illegal working laws with greater ease."
The spokesperson added that there would be a consultation with employers and trade unions over the immigration officers' powers.
The bill makes clear that the immigration officers will have the power to search and arrest illegal workers where they have reasonable grounds for suspecting an offender is on the premises. The bill also states that contractors will have no say in the matter. It says: "Employers would not be able to refuse immigration officers entry to business premises."
Employers would not be able to refuse immigration officers entry to business premises
Extract from immigration bill
A spokesperson for the Construction Confederation welcomed the move as a positive step in preventing illegal workers operating within construction.
But he warned that the implications of these new powers would have to be carefully assessed.
UCATT general secretary George Brumwell said the Home Office's strategy would deter employers from introducing cheap, illegal labour on the quiet and ensure that foreign workers who were here legitimately were not exploited. He said: "Action taken by immigration officers would stop foreign workers from being exploited in the labour market."