More than four out of 10 fines imposed on companies for hiring illegal workers remain unpaid.
Of the 3,164 illegal labour penalties handed out to firms – mainly restaurants and takeaways – by the UK Border Agency over the past 18-months, 1,301 have yet to be collected.
About £6.5m in fines are believed to be outstanding, while the average fine imposed on guilty employers was £5,000, half the maximum penalty.
Chris Huhne, the Liberal Democrat home affairs spokesman who released the figures, called on the government to tighten fine-collection procedures to ensure firms could not flout the rules, the Daily Telegraph reported.
He said: “The government has belatedly got round to identifying unscrupulous employers who profit from the exploitation of illegal workers. It seems when they do find them there are no guarantees that they can get them to cough up any of these profits.
“We need to clamp down on rogue employers and the only way to do this is to make sure that they pay the fines they are given.”
A Home Office spokesman said: “We are determined to crack down on illegal workers and those who employ them, and the civil penalty system is one of the ways we are doing that.”
The civil penalty system was introduced in February 2008 and forced employers to pay a sliding scale of penalties based on how diligently they researched their employees’ backgrounds.
The spokesman added: “Since the system was introduced… we have issued over 3,000 fines and recovered millions of pounds. The majority of unpaid penalties are still subject to objections and pending appeals.”
In August the UK Border Agency revealed that restaurant chains including Pizza Hut and Chez Gerard, and the oil firm BP, were among the firms fined under the new rules.