The TUC and NUS are concerned that interns around the UK are being exploited through unpaid work. Unions fear that many employers have sought to take advantage of graduates' desperation to find work in the economic downturn and so see interns as a useful source of free labour. Others may be unaware that non-payment of interns is a breach of the law and of national minimum wage rules, warns the TUC.

The event today (Monday) will feature contributions from the TUC, NUS, campaign groups and interns themselves, and the TUC will also launch a 'Rights for Interns' Smartphone application. The phone app can be downloaded to Apple and Android phones free of charge. It features tools to help interns evaluate their own internship, or ones they are considering, as well as general guidance on work rights they are entitled to and minimum wage rates. Interns who think they should be paid can use the app to find out what they are owed.

Hazel Blears MP will address the seminar on the parliamentary intern scheme, and other speakers include TUC Deputy General Secretary Frances O'Grady, NUS Vice President (Society and Citizenship) Dannie Grufferty, National Union of Journalists (NUJ) General Secretary Michelle Stanistreet, representatives from support group Intern Aware, and interns who have experienced exploitation.

Any intern who is undertaking work-related tasks, with set hours and a duty to turn up and do the work is probably defined in law as a 'worker' and, as such, is eligible for the minimum wage, working time and paid holiday rights. The TUC believes any internship that does not simply involve observation and work shadowing should qualify for payment.

As the use of internships becomes more widespread, the TUC is concerned that jobs in popular career destinations like journalism, advertising, film, television and public relations are becoming an exclusive domain for people from affluent backgrounds. Only those young people whose parents have the means to support them - often for months on end - can afford to work for free, says the TUC.

Frances O'Grady said: "Whether they are unscrupulous or genuinely unaware of the rules, too many employers are ripping off young people by employing them in unpaid internships that are not only unfair but, in most cases, probably illegal.

"Internships can offer a kick-start to a career that many young people value. But as more and more graduates are being forced to turn to internships in place of traditional entry level jobs, we're concerned that a growing number of interns are at risk of real exploitation.

"It is vital that we crack down on those internships that offer little but hard graft for no reward. Employers need to know that there's no such thing as free labour."

Dannie Grufferty said: "Unpaid internships quite flagrantly do not comply with basic minimum wage legislation. They are not only deeply unfair, but are straightforwardly illegal.

"If we are serious about fair access to all professions, the current situation whereby young people are expected to undertake many months, and sometimes years, of unpaid work in order to be seen to have sufficient experience simply cannot go on. This presents a fundamental barrier to many of the most competitive professions for the millions of young people who cannot afford to work for free.

"With over a million young people unemployed, we need to be clear now more than ever that young people's enthusiasm and desire to work cannot be exploited. A fair day's work always deserves a fair day's pay."