The problem was most recently highlighted by the EU ombudsman Emily O'Reilly who raised concern about unpaid internships within the European External Action Service (EEAS).
On Tuesday the campaign will again be in the spotlight when Parliament's youth intergroup - which campaigns to raise awareness about unpaid interns - holds a special event.
It plans to hold a special screening of a documentary which depicts the situation of interns in the EU institutions.
German MEP Terry Reintke, who is co-Chair of Parliament's youth intergroup, is hosting the event. The screening will be followed by a panel discussion with the directors, Sabiha Kapetanovich and Francesco Baiocchi.
Reintke, a Greens MEP, said, "The reality is that there have always been unpaid internships in Brussels and in other EU institutions such as the EEAS."
According to a survey among interns in the European Parliament, which the youth intergroup conducted earlier this year, almost half of the 233 respondents get an allowance that is below the cost of living in Brussels and one in 10 said they did not get any compensation for their internship.
Reintke, who is the youngest female MEP, said, "What we have seen throughout the last months is that there is a growing acknowledgment that not paying your interns is plain unfair.
"Whether or not young people get the opportunity to experience work at an EU institution cannot depend on the wallets of their parents. By not paying for an internship, some people are directly excluded from the opportunity to even do such an internship as they won't be able to cover their living costs."
She added, "We call on all international institutions to abide by the legal standards which apply to the place where the internship is performed. For interns in the European Parliament this would mean that they should have a right to the Belgian minimum wage which also applies to interns in Belgium.
"In our #FairInternships campaign we also call for quality minimum standards for internships."
This means, she said, that there should be a learning agreement, interns should have the right to their own workplaces and there should be the chance for an evaluation and direct feedback.
The MEP believes it is "really great that interns in Brussels are uniting and trying to make their voices heard.”"
She added, "I strongly support their claims and I will continue to fight for every intern to be paid at the EU institutions as well as at all other places of work."
The campaign is also backed by Portuguese MEP João Pimenta Lopes, GUE/NGL group coordinator on the employment and social affairs committee, who called on the EU to "put an end to precarious work and seriously restrict the use of short-term and partial time contracts."
In 2016, the European Parliament recruited 118 candidates under its training placement scheme and also hired 505 university graduates.
A Parliament spokesperson said, "Parliament offers several options for traineeships within its secretariat to provide opportunities for vocational training and for learning more about what the Parliament is and does. There is a distinction between 'graduate traineeships' and 'standard' or 'educational' traineeships."