Green Party leader Caroline Lucas also said her party would create up to one million new jobs through investing £44 billion in green industries.
Lucas's comments came in the second of a series of question-and-answer sessions posted by the leaders of all the main political parties on social networking site The Student Room.
Lucas said the National Minimum Wage should be a "genuine living wage", at 60% of net average earnings. At current rates, this would come to £8.10 an hour - 40% higher than the current highest rate of £5.80 an hour.
Responding to a question about the prevalence of unpaid internships, Lucas said: "It's true that more young people than ever now find themselves having to work for nothing in order to get a foot in the door. Work experience and internships can be a genuinely useful way of finding out more about your chosen industry and showing that you are committed to working hard for little or no reward. But naturally, this can give those from wealthier backgrounds an unfair advantage.
"It goes without saying that internships and work placements should always offer fair expenses to cover travel and food. It may also be beneficial to limit the number of unpaid internships that one person can do, in order to make it a fairer marketplace for those who can only afford to do one. The Green Party would be keen to follow best practice advice on this from industry and employment specialists, and student welfare advisers.
"In the longer term, the Green Party is calling for the introduction of a universal Citizen's Income, which would give everyone the financial flexibility to, for example, undertake unpaid internships and work placements. We also support a National Minimum Wage that is a genuine living wage, at 60% of net national average earnings to help those working in part time or low wage jobs."
She also called for state funding of political parties to help smaller parties employ paid staff as well as the setting up independent bodies to help form decisions on drugs policy, workers' rights, animal welfare and ethical research.
