There's an implicit message in the government's new immigration rules: employers better get tough with illegal workers or the government will get tough with employers - issuing hefty fines of up to £10,000 to organisations with insufficient procedures in place to track migrant workers, or even putting individual HR directors behind bars.
"The immigration service is putting the burden on the employer - that's the whole focus of this new system," says Julia Onslow-Cole, partner and head of global immigration at the legal division of business services company PricewaterhouseCoopers, PwC Legal. "This is not just a mere threat, I think that we will see a number of high-profile prosecutions of employers in the next 12 months," she adds.
As of 29 February, employers must now not only check the status of all new permanent and temporary staff they employ, which was the case under the previous legislation (the Asylum and Immigration Act 1996) now they must, on an annual basis, re-check all those migrant workers without permanent residency to verify the status of their right to live and work in the UK.
On the face of it, the increased burden on employers appears little more than an administrative one - perhaps beefing up databases to flag up the employees who need re-checking and when, or maybe more HR staff time allocated to doing it.
"As an employer you are not expected to break fraud rings, it's a case of checking names and photos," says Sikin Andela, partner for law firm Glovers. "I've seen nothing under the Act that shows such a high burden of proof on employers to go to specialist agencies to authenticate documents, just check to a reasonable level."
That's certainly the approach being taken by food and support services company Compass Group, which recruits about 30,000 people a year. But the new immigration rules mean that the company doesn't just have to check out existing employees, but people who are simply applying as well, according to the company's resourcing director Vicky Williams.
"We already had a robust system in place [under the old legislation], and we've gone the route of empowering our hiring managers to check this documentation. We've provided training internally and have hints and tips on our intranet to show pictorially the kind of documentation they need to see," she says.
And while employers can access document verification hardware and software to automate the process to some degree, the internal processes of some organisations will doubtless be challenged, believes Onslow-Cole.
"In some small organisations it's likely to be quite burdensome, while in large organisations it can be a problem because there are lots of people with overlapping responsibilities," she says.
But if clarity of responsibilities or staff time presents a challenge, so too does another aspect of the new legislation that, although not stated outright, is implicitly required: the acquisition of knowledge about employees' personal circumstances.
In the case of migrant workers whose visas are contingent upon their partners' residency, the annual check will involve not just re-examining documents, but asking sensitive questions about whether they're still married and, if so, is their spouse still employed under the terms of his or her original visa. HR must be prepared to ask probing questions to be compliant, says Tracy Evlogidis, head of immigration for solicitors Speechly Bircham, "however uncomfortable they may feel, to avoid personal liability HR officers need to do it".
Williams believes the burden remains greatest at the point of recruitment, as, once someone is on the books, it's simply a case of re-checking them every year.
"We've built our database in-house to allow a flag to appear 11 months later," she says. Buying in screening services to authenticate documents may be an attractive option, but for many employers it is cost prohibitive.
"The Home Office provides some very good documentation," says Williams. "It's perfectly sufficient and it's not advocating that you outsource."
Even where employers and agencies have followed the law, they could still end up with illegal workers on their payroll who slip through checks with fraudulent documentation. That's always been the case, of course, but for many employers, the main concern with the new rules is not so much about the increased administrative burden, but the expectation of a government crackdown on illegal workers.
Onslow-Cole explains: "Employers are now worried by their past history, and they should be. If you think you had good checks in place before, and you did checks when people were hired, then fine. But if you didn't do them properly, you're not absolved from the old law simply because the new law is in place."
And organisations that rely on agencies to supply large numbers of temporary staff are also vulnerable, for the end employer is liable in the eyes of the law.
David Leyshon, managing director of recruitment agency CBSbutler, which specialises in placing permanent and temporary staff in IT and engineering, says: "We are taking a large part of the burden in doing the checks. That's part of the overall service we deliver." He believes most employers will want to do the bare minimum as required under the new regulations, but says those working in the public sector "are likely want to go one step further" as the fear of bad publicity from a raid on illegal workers will simply be too great.
Pre-employment screening providers advocate what Charles Thomas, consultant for screening company Kroll Background Worldwide calls a more "belt and braces" approach.
"Often the lowest level staff pose the highest risk to companies," he says. "But because they're coming in at a lower level, it's not seen as cost effective to do comprehensive checks, as [they would with] a director on a six-figure salary. Yet the risk is the same if not worse with regard to people cleaning the floors."
Aside from the reputational cost, there's the potential operational cost of losing dozens of staff overnight, adds Thomas.
"The new legislation is prompting employers to do more risk assessment of their workforce - and that's a good thing."
Whatever their response to the new legislation, employers should be certain of one thing: expect more of the same as the government continues with immigration reform. The Border and Immigration Agency is still refining changes to the system of sponsoring migrant workers, and it seems employers will face an even greater burden with regard to employee monitoring, according to Evlogidis.
"It's not just carrying out checks, it's an ongoing policing system that will be time-consuming and costly," she says.
Jonathan Cray, managing director at Control Risks Screening, agrees: "The pressure of work on HR departments is going to go up," he says. "They run the risk of taking their eye off the core business, which is managing people and employment." In the circumstances, HR directors may be well-advised to carry out a risk assessment sooner rather than later.