Up to 1000 cleaning contractors will be audited by next year in a bid to catch shonky operators who underpay workers.

The Fair Work Ombudsman today announced the random audits following concerns over a high level of non-compliance with fair work practices by cleaning contractors.

United Voice, the union representing cleaners, welcomed the audits, saying major corporations such as Westfield also needed to take some responsibility if they employed shonky contractors.

The ombudsman said in a statement that inspectors had recovered hundreds of thousands of dollars for underpaid cleaners over the past three years.

Auditing of 376 cleaning businesses in 2010 found 149 were non-compliant with federal workplace laws.

The most common contraventions were underpayment of penalty rates, inadequate record-keeping and failure to keep to minimum shifts.

Fair Work Ombudsman Nicholas Wilson said the 2010 results and ongoing complaints from the sector prompted the decision to undertake a follow-up campaign.

"We are mindful that this is an industry which employs large numbers of young people and migrant workers who may be vulnerable if they are not fully aware of their workplace rights."

United Voice National President Michael Crosby said the audits were a shot across the bows of major corporations like Westfield, which was one of the largest users of contract cleaners in Australia.

"Underpayments, cash payments, short shifts, bullying and sham contracting are rife in this industry," Mr Crosby said in a statement.

"These contractors don't operate in a vacuum. They are in business because of the refusal of property owners to accept responsibility for the consequences of their contracting decisions."

Mr Crosby said the ombudsman had recently warned business operators they risked breaching workplace laws if they knew underpayments were occurring.

AAP