Nearly half a million people are employed in developing countries earning virtual goods in online games to sell to players, a study has found.

Research by Manchester University shows that the practice, known as gold-farming, is growing rapidly.

Researchers say the industry, which is largely based in China, currently employs about 400,000 young people who earn 80 per month on average.

Games companies have attempted to crack down on the practice. Players in the popular online game World of Warcraft acquire virtual gold by fighting monsters and completing quests.

Alternatively, some simply buy it from a fast-growing workforce employed to play this and other games.

Manchester University says the young people, described in the study as "playbourers", sell gold or other virtual goods, despite the practice being against the rules of many online games.

However, the report's authors say an industry which connects cash-rich time-poor players with those willing to work long hours for little reward is likely to go on growing. More PlayStation 3 News...