Sainsbury's has apologised for advertising for an artist prepared to decorate a staff rest area for free.
The ad, placed in the Camden New Journal, asked for 'a creative and an ambitious artist to voluntarily refurbish our canteen'. The job would, it said, give the successful applicant 'the one opportunity to build your career and develop your reputation'.
But candidates haven't been impressed. "I am looking for a company worth £150,000,000 to feed all of my artist friends in Manchester,' writes artist Conor Collins on Twitter. "This is a once in a lifetime opportunity to do work for absolutely free but don't worry, you will get plenty of 'experience', chances to 'build your career' and 'develop your reputation'."
Another ominously offers to carry out the decoration 'with my own style'.
Sainsbury's has apologised, saying the ad was a mistake, and says it plans to have a quiet word with the store. "It is not our policy to hire volunteers, and we are sorry for this error of judgment," it says.
Goodness knows, artists earn little enough even when they do get paid. According to a-n, the Artists Information Company, most British artists earn less than £10,000 a year from their work.
The law is clear that anybody who works should be paid - unless they are volunteering for a charity or government institution. This is how ZSL London Zoo was able to get away with advertising for an unpaid intern with a master's degree late last year.
The six-month post helping to run a global conservation project, it said, would attract £5 a day plus a travel card.
Beyond this, unpaid internships are technically illegal, even if expenses are paid. The exception is if the role involves observing only, rather than carrying out actual work.
But if you're required to work for a minimum number of hours and set tasks, and if you add value to a business, then you're entitled to the national minimum wage.
And, points out Tanya de Grunwald of jobs website Monster.com, you don't get any say in the matter.
"You don't have the right to waive your wages, even if you say you'll accept experience as payment," she says.
"The minimum wage isn't just there to prevent those who do the jobs from being exploited - it's also to protect poorer applicants from being excluded from competing because they can't work for free."