Immigration Minister Brendan O'Connor admits his controversial claim that more than 10,000 foreign workers are rorting the 457 visa program was guesswork.
Mr O'Connor said earlier this week that he believed about 10 per cent of the 107,000 people working in Australia on 457 visas were abusing the scheme.
The opposition and business groups have challenged the claim, accusing the minister of ramping up a Labor fear campaign. The government announced a crackdown on the 457 scheme in February.
Now an immigration department discussion paper released under freedom of information laws has emerged, which says rorting of 457 visas is actually rare.
Mr O'Connor has denied he exaggerated the rort claims.
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Asked how he came up with the 10,000 figure, Mr O'Connor said he was asked to give an estimate.
"I'm making a forecast like others have made forecasts," he told ABC Radio on Friday.
"We don't have an exact precise figure."
He would not apologise for "fixing a scheme that has problems."
Mr O'Connor said there was evidence the growth in the 457 program was out of step with skills shortages in specific industries.
