Legal status is no guarantee that migrants will find more security in the workplace, according to a new study published in the journal Migration Letters.
Researchers interviewed around 200 migrants across Europe in a bid to find out whether regularisation - the process by which an immigrant obtains legal right to work - affects work conditions and opportunities.
It was found that although around 90% of the documented migrants surveyed worked in the primary sector, many reported issues such as employers not declaring their hours of work to the authorities in order to avoid contributing to tax or social insurance pay-outs. These issues were particularly prevalent in areas like cleaning, construction and agriculture.
Few regularised migrants chose to work in the informal sector because their employers preferred to offer work to those presenting themselves as undocumented, as they avoided having to comply with employment laws. Others chose informal work because they saw it as offering more freedom and, additionally, their earnings were not subject to taxation.
The research also found that because regularisation often depends on an endorsement from an employer, it often means workers feel unable to challenge employers who ignore labour laws.
In some cases, interviewees found that employers were less willing to employ them when they had legal status. In the case of those participants from the UK, only a minority found that a change in legal status resulted in improved employment conditions.
Co-author Dr Anna Paraskevopoulou, Senior Lecturer in Human Resource Management and Leadership at Anglia Ruskin University (ARU), said: "Around 40 regularisation programmes have been implemented in Europe and the United States, and more than five million people have been regularised since the 1980s.
"Our study found that while immigration policy does play a part in determining the rights of an individual, the labour markets themselves play a crucial role in creating spaces for undocumented workers to live and work in a country.
"In speaking to these migrants, an alarming finding emerged that even though some had secured legal status, they remained trapped somewhere between formal and informal labour markets, working for employers who would not pay them for their actual hours, or failing to make necessary social security contributions.
"Regulation in itself cannot eliminate inequality - we cannot underestimate the roles played by weak trade unions, glass ceilings, and a weakening of employment law."
The study also involved Dr Eugenia Markova from the University of Brighton and Professor Sonia McKay from the University of Greenwich.