British business is making big money out of illegal immigration, the chairman of the influential home affairs committee has said.
Illegal immigrants are meant to be deported
John Denham said the authorities were not tough enough on firms who "fiddled" the tax system by employing illegals.
And it was not just small operators but "household names" that were guilty.
Illegal immigration into the UK would never be tackled until such companies were brought to book, the ex-Labour minister told the BBC.
"It is very clear there are people in this country making money out of illegal immigration," Mr Denham said.
"I suspect unless we get after people making money out of it, including some very respectable household names, we will not make progress."
On Tuesday, immigration chief David Roberts came under fire after he told Mr Denham's committee he did not have the "faintest idea" how many illegal immigrants were in the UK.
He said individual illegal immigrants were no longer pursued unless they were thought to pose a threat to national security.
And resources were concentrated instead on raiding companies that employed them, often in the food processing, construction and catering industries, although only 293 people had been successfully prosecuted in the past year.
But Mark Bolyeat, who represents employment agencies which supply casual labour to the food industry, told the committee immigration raids were often seen as a publicity stunt, with workers being back at their jobs within hours.
"They are great for TV, and there was one in Scotland which was on TV, and my member phoned up from Scotland in the afternoon laughing, saying the workers were all back at work, having been arrested and on the news," he said.
Mr Bolyeat told the committee the tax authorities - rather than the Immigration and Nationality Directorate (IND) - should mount raids, as firms employing illegal immigrants generally did so to cut down on their tax bill - and most thought they would not be pursued for it.
"As long as somebody running a food factory believes he can get away with it, they will continue to do so because they are under such cost pressures from the supermarkets they have got to try and make a living," he told the MPs.
He said one labour provider told him "I have started paying tax and national insurance in the last year but I am about to go bust and that's the position that some of them find themselves in, do they wish to be in business or not?"
He said "going after individual labour providers was not likely to be effective" and it was "far better to go after their customers".
"I have given names and addresses to the tax authorities of large food plants I know are evading tax because the rates they are offering my members are not enough to enable the legal minimum wage to be paid.
"And I think if the Revenue went into these organisations with a big van, saying 'revenue investigations department' they would disrupt those businesses first of all because many of the workers would be out the door."
Tax evasion of this kind was costing the UK anything up to £1bn a year, the committee was later told.