In an anonymous dispatch, one graduate tells of her experience in the charity sector, where those campaigning for better ethical standards don't always see a need to offer pay

In July, I was at an interview for a three-month unpaid internship at a campaigning organisation in central London which specialises in using public and shareholder pressure to push corporations to become more ethical.

"What exactly would I be doing?" I asked my interviewers. They explained that the intern would work mainly on a campaign for corporations to pay all employees a living wage (£8.30 an hour in London). Didn't they find it a bit ironic, I asked, that they were looking for an unpaid intern?

"Oh," said my interviewer, looking surprised. "That's a really embarrassing question."

In June, I had returned from a two-year stint working for VSO in Cameroon. I'd been running projects, managing budgets, organising workshops and training, and earning a local-level salary. I loved working in international development; I'd had a great post-placement evaluation of my work. I also had a good degree from Cambridge and plenty of voluntary experience. But I had reckoned without the hurdle of the unpaid internship. If you don't have the right connections pretty much the only way to start a career in a UK-based international development role is to spend months and sometimes years as an unpaid intern. To get one of these internships (some I was interviewed for had more than 100 applicants) you can need years of experience, and preferably a master's degree.

I was invited for seven interviews at NGOs with annual budgets ranging from £500,000 to more than £5m. Two were human rights organisations and three focused on working for greater corporate responsibility, and campaign explicitly for improved workers' rights. They all expected their intern to stay for at least three to six months and work two to five days a week. None offered payment. Using unpaid interns to fill out the entry level of the charity sector has become endemic. This Last week, the UK's largest charity recruitment site, charityjob.co.uk, was advertising 61 internships. Only two were for paid interns. Many were for purely admin-based positions such as "database intern" and "receptionist intern". After one of my unsuccessful applications to a human rights organisation, my interviewer told me that although she had been impressed by my skills in activism and mobilisation she "had to pick someone who had a stronger background in using databases and other administrative systems".

The minimum wage is being undermined because young people are so desperate for experience that they are prepared to work for free. Careers services tell them that unpaid internships are the only way into certain sectors. It has reached the point where many entry-level jobs no longer exist because all the work is being done by overqualified interns. There are now more young people out of a job in the UK than at any time since records began, according the Office for National Statistics. Unpaid internships are part of the problem.

The world of unpaid internships shouldn't be confused with work experience or paid internships. Work experience is a placement of a week or two where you go to an office and see how it feels. Paid internships can be a recruitment strategy to attract potential employees.

In 2008, I won a place on a corporate social responsibility scheme run by Goldman Sachs. It was designed to identify future "global leaders" with an interest in social issues and nurture their talents, while simultaneously inculcating them with a healthy respect for Goldman Sachs and its job opportunities. Along with 75 other undergraduates from all over the world I was flown to New York for a programme of cultural events, talks on global affairs, lavish dinners and multiple presentations about Goldman Sachs. I was paid $3,000 for one week. I decided I had no interest in working for a business that thought throwing $3,000 at an undergraduate was the best way to run a corporate social responsibility scheme.. Nevertheless it was a good insight into the time and money corporate giants are prepared to invest to attract the best and the brightest.

Bright young people who want to work in the charity, arts or media sectors (some of the most consistent users of unpaid interns) accept that they are never going to be paid the level of wages on offer in investment banking, the law, or management consultancy. On the other hand, as my interviewers from the living wage campaign were so eager to point out, people have a right to a living wage for the work they do.

In many local authorities interns are classified as "not available for work" and cannot claim jobseeker's allowance. People face a Hobson's choice between not interning and still receiving benefit, and interning to get experience and having their benefit cut off. Entire professions are blocked off from any young person who cannot afford to live without an income.

There is a middle way between Goldman Sachs-style profligacy and being paid nothing at all. At a summer internship for a bank specialising in charity clients, I was paid £7.50 an hour to work in the ethical and responsible investment team: this was less than an entry-level salary, but enough to make the experience affordable. The organisations that have "raced to the bottom" and populate their offices with unpaid interns will never be able to attract the diverse range of young talent available to those that recognise their value and pay them at least the minimum wage. Unpaid internships are a privilege reserved for people like me with parents who live in London, or for those whose parents are able and willing to support them financially. I've also been able to find a flexible paid job for my local council, doing care work during the evenings, early mornings and weekends.

Unpaid interns undeniably look great on an organisation's budget sheet. "They're like programme assistants, only we don't pay them," I've heard people say in my current workplace, where I work unpaid four days a week.

Whether interns are effective staff members is more questionable. They move on after a few months, so there is a limit to how much responsibility they can be given and how much time an organisation is willing to invest in their professional development.

Despite my objections to the pervasiveness of unpaid internships, I am as culpable as any other intern or organisation that buys into the system by participating in it. I once went for an interview for a position at Anti-Slavery International, the world's oldest international human rights organisation, which has been campaigning against unfair labour conditions for 172 years. They were not planning to pay me.