Premier League football clubs have been accused of "unfair and exploitative" practices after advertising for young interns to work as highly qualified performance analysts without pay or expenses for 12 months on the website of a government quango.

As the government referred 100 companies for investigation by HM Revenue and Customs after a campaign group told ministers they might be breaking the law through their use of unpaid staff, the Independent Parliamentary Standards Authority also admitted it had suggested to an MP that she use unpaid interns to cover staff shortfalls.

Football clubs including Reading, Wigan and Swansea have all advertised for interns to work unpaid for an entire season to film training and matches, input data and analyse the performance of individual players.

The adverts appeared on the website of UK Sport, the quango that will receive £500m in exchequer and lottery funding over the next four years to fund elite Olympic sport.

While making clear it did not vet the adverts from sporting organisations appearing on its site, UK Sport said it would meet next week with campaign group Intern Aware to discuss the issue.

"It's not about the amount of money in the company, it's about the culture and if there's a demand for young people to break in then it makes it worse. Sport is a good example. Companies are thinking 'why bother paying someone if you can get someone for free'. It's not only exploitative but it's exclusive. How much must it cost to work in Reading for a year for nothing? They are narrowing it down to a tiny group of people," said Intern Aware co-founder Gus Baker.

"It's a waste. They are advertising for people doing a real job analysing first team performance and feeding it back in. I don't know why they don't want to pay to get someone decent to do that job for them. It's self defeating as well as unfair and exploitative."

In the case of Reading, it advertised for a "performance analyst intern for the 2013/14 season" with a postgraduate degree in performance analysis or sports science, experience of working in professional football and experience of using the main software packages.

It says the successful applicant will be required to work "unsociable hours" and "attend all first team home games and some away games".

Wigan, who play Millwall at Wembley in the FA Cup semi-finals this weekend and stand to benefit from a share of the Premier League's new £5.5bn TV deal if they avoid relegation, advertised for three unpaid interns for the entire season.

"Hours of work will be flexible and will include weekends and some evening work," added the advertisement.

Wigan, who declined to comment, have a customer charter that states: "The Club is an equal opportunities employer and is committed to an equal opportunities policy and actively works throughout the local community promoting social inclusion campaigns."

Swansea City, who have received plaudits for their careful housekeeping and an ownership model that gives fans a 20% stake, recently advertised for a highly qualified, unpaid performance analyst to work for 11 months, shortly before announcing a £2m dividend to its owners.

The issue came to light in the same week that Professional Footballers' Association chairman Clarke Carlisle called on clubs to break open football's "closed shop" and recruit from a more diverse range of backgrounds.

"It's incredibly difficult and about time people acknowledged that it [football] is a closed shop. People try to keep a lid on it but that's the truth," said Carlisle, who was speaking at a Kick It Out conference.

It was Intern Aware that prompted the junior employment minister, Jo Swinson, to hand the names of 100 companies – which have not been made public but believed to include several household names – to HMRC for investigation.

While companies are free to offer work experience, where this ends up amounting to a job – for example if hours and duties are set and the position lasts for a long time – companies are breaking employment laws if they do not pay at least the minimum wage.

Aside from the illegality, critics say the use of long-term, unpaid positions as an entry point to popular professions in effect excludes those without well-off parents or other means to support themselves.

MP Stella Creasy said she approached the IPSA to make the "business case" to add to her five staff, due to greatly increased casework and reduction in other advice services available to Walthamstow residents.

The IPSA accepted her case but said it was not their place to address shortfalls in other public services. The Labour MP said she was "gobsmacked" to then be told: "You could streamline your processes, you could delay responding to people, you could use generic responses, you could not respond to everybody, or you could use unpaid interns."

An IPSA spokesman said that it offered Creasy £3,000 a year extra on top of the normal £144,000 staffing budget for each MP but that she wanted more.

"Towards the end of the conversation somebody here said, 'Look, things you might look at are how you run processes in your office, can you streamline them, could you complement your staffing provision with interns?' She was also told that none of these were recommendations and we couldn't advise her how to run her office."

Reading FC argued that internships were a fact of life and enabled ambitious "youngsters" the opportunity to gain experience.

"Many young people, however well qualified, find it very hard to obtain their first job because they do not have experience. Internships give these youngsters the opportunity to gain practical experience, thus enhancing their job prospects considerably. This season we received countless unsolicited applications for internships and formalising the process has been of great benefit to both sides," said a spokesman.

"For many years, a huge number of organisations in all types of sectors have offered internships – for example it was said recently that 8 out of 10 new journalists started their career in this manner. Companies continue to do so because they give genuine experience in a work environment. Indeed, a number of young people with intern experience have gone on to become permanent employees at our club, and another one signed his full time contract just this week."