Unpaid internships in industries ranging from fashion to politics are costing youngsters more than £1,000 a month in London amid rising rents, a new study reveals.

The Sutton Trust estimates that 10,000 young people take up an internship a few months after graduating,  around a fifth of which are unpaid, although the high cost of living in the capital is likely to be pricing out those from low and middle-income families.

The education charity said it is concerned that the “significant costs” associated with unpaid internships are shutting many less-advantaged young people out of careers.

Unpaid internships costs a single person in London more than £1,000 a month, and £827 in Manchester,  the study found.

Costs in both cities have increased since the Trust last carried out a similar study in 2014.

Examples of unpaid internships advertised online this month include a major fashion designer wanting someone for up to three months in the lead-up to London Fashion Week, and an MP offering only expenses for a researcher, said the report.

Sir Peter Lampl, chairman of the Sutton Trust, said: “Around 40% of young people who have carried out an internship have done so unpaid. All internships over four weeks should be paid at least the minimum wage of £7.50 per hour.

“Failure to do so prevents young people from low and moderate-income backgrounds from accessing jobs in some of the most desirable sectors such as journalism, fashion, the arts and politics.

“All internship positions should be advertised publicly.  Large numbers of internships are never advertised and instead offered through informal networks.

“This practice locks out young people without connections.  Also, the process by which potential candidates are selected for internships should uphold the same standards of recruitment as for other jobs.”