A British conservationist is leading an audacious plan to create a chain of man-made islands in northern Sumatra that would liberate the Indonesian island's population of caged orangutans.

Dr Ian Singleton aims to create four islands of grass, shrubs and trees for sick and injured orangutans – those who are unable to be reintroduced to the natural habitat – to roam, freeing them from the 3x4m cages in which they currently reside.

Singleton is currently in the process of securing land for the islands. The ideal location would be near the coast with a consistent supply of fresh water via a stream or river.

Diggers, operated by local contractors, will then carve up the land to create moats, thereby encircling the land with water. The earth removed by the digging will be used to landscape the islands to make them ape-friendly.

Orangutans, which can't swim, will be reluctant to leave the islands due to the water, although Singleton plans to erect an electric fence to ensure the creatures don't drown.

"Depending on the site, it shouldn't take us too long to create the islands, as long as the moats don't leak," Singleton told the Guardian from northern Sumatra.

"The biggest challenge is finding the right land that has the right security and a water supply that isn't full of effluent."

"Finding a clean stream in Sumatra can be difficult as there's lots of pollution, but we have the option of creating a bio-filtration system to purify the water."

Singleton and his team have released more than 150 orangutans into the wild over the past decade, but currently have 50 further apes in medical quarantine.

A handful of orangutans have been earmarked for immediate transportation to the island, including twins that made headlines earlier this year due to both of their parents being blind.

Singleton has been in Sumatra since 2001, following stints at zoos in Jersey and Edinburgh. He leads the Orangutan Conservation Programme in the country and is funded by a Swiss NGO, PanEco.

While the immediate aim is to protect the captive orangutans, Singleton hopes the project will inform local people about the threat to the animal's survival via an education centre and guided walks.

There are only an estimated 6,000 orangutans left in Sumatra, due to deforestation and conflict with humans.

"These orangutans are refugees from forests that don't exist any more," he says.

"You have animals like Leuser who has been blinded by an air rifle and you don't want him living for 45 years in a small rusty cage. I want people in Medan (capital of the north Sumatra province) to see how these orangutans have been shot or had their arms chopped off or got hepatitis B."

"There needs to be a change in behaviour, otherwise the project is a waste. It's all very nice getting westerners here, but we need to reach the people who are chopping down the trees here and shooting the orangutans because they're in their habitat."

"Lots of middle class people, even policemen, steal orangutans and have them as a status symbol. The irony is that the people who are meant to uphold the law here are the ones with orangutans in cages."

Singleton says that he is close to acquiring a 20 ha (49.4 acre) plot of land to create the islands, but claims he has been hindered by the byzantine Indonesian system.

"I fluctuate between cautiously optimistic [and] very pessimistic," he says. "The business lobby is so powerful here and vote buying so prevalent, that it's hard to change anything.

"One minute the government will say that it wants to protect the forest and then they will grant a permit to clear 15,000 hectares of forest. Very few people are prosecuted for keeping an orangutan as a pet."

Singleton is working with the Australian Orangutan Project to raise funds for the island development.