As one charity last week warned thousands of gap-year travellers that their volunteer holidays may be spurious and badly planned, further evidence has emerged of placement agencies charging high fees from travellers wishing to work in the developing world.

Kate Hardyment from London applied directly to the Ghanaian work-camp project Volu, paying £135 for her four-week stay. On arrival, she found other volunteers had paid UK-based agencies up to £1,000 for identical placements – a mark-up of 600%.

Placement agencies justify the disparity by providing support services such as overseas staff, 24-hour helplines and predeparture orientation courses, but many volunteers claim this isn’t worth the extra cost.

Travellers Worldwide charges £995 for a month’s placement in Ghana. Of that, about £40 goes into a charitable trust and an undisclosed sum goes towards food and lodging. The rest, says managing director Mike Ecclestone, is eaten up by overheads.

One of the most successful UK agencies is I-to-I, owned by the holiday giant First Choice, and the company freely admits that it is in business to make a profit.

“We are a tour operator, and we facilitate volunteering by finding sustainable projects worldwide and sending people to take part in them,” said the company’s Jo Little.

I-to-I offers four-week placements in Ghana from £795. Asked to justify the additional cost of several hundred pounds, Little said: “What you are paying for is the service you receive. Yes, you can do it a lot cheaper by going direct, but we provide security, peace of mind and a hand-holding service for those who haven’t travelled alone before.”

Volunteer Josh Everard also went direct. “I can understand why people would want that backup, but in my case, the only difference was a 24-hour helpline and a T-shirt,” he said.

Last week, the international development charity VSO advised young people who are taking a gap year abroad that it may be better for them to travel rather than take up voluntary work in developing countries.

Recent reports have revealed a number of projects to be somewhat less than worthwhile. These include a cheetah-tagging project in South Africa using inert radio collars and a turtle census in Central America that counts the same turtles every week.