Bardsey Island is an ancient pilgrimage site
Electricity and flushing toilets would spoil the spirit of the unique island of Bardsey, it has been claimed.
Former guardians of the so-called island of 20,000 saints off the north Wales coast are worried by plans to bring it into the 21st Century.
BBC Wales' current affairs TV programme Taro Naw, broadcast on S4C, also highlights concerns that local people are losing their grip on the running of the island, at the tip of the Lleyn Peninsula.
The criticism by the former Bardsey Island Trust members follows a £2m modernisation programme recommended in a report commissioned by the trust.
In ancient times the island was an important pilgrimage site and legend has it that thousands of monks are buried there.
It was bought in 1979, but the trust established following its purchase has been faced huge financial losses in the last few years.
A new report recommends a number of measures to attract more visitors and increase revenue.
Actor Mici Plwm: "It would be a great pity"
They include installing electricity, flushing toilets and turning one of the houses into a B&B and converting a barn into a bunkhouse.
Actor and former trust member Mici Plwm, who has been a regular visitor to the island, said: "It would break my heart if they went too far in developing Bardsey - it would be a great pity."
Former farm tenant Gareth Roberts helped run the island for seven years until 2001.
"I have no confidence in the current trust council members," he said.
"There is not enough local knowledge involved with running the Island.
In 1986 the island became a national nature reserve
The trust - which is run on a not-for-profit basis - said it was trying to increase visitor numbers while maintaining the atmosphere of the island.
Trust chairman Chris Arnold said: "At the moment we aren't coming anywhere near the cap of one thousand visitors a month placed by the Countryside Council for Wales.
"I think we would have to work extremely hard to get to that and indeed we are not seeking to.
"We have responsibilities here and a desire and duty to allow people to get the island and a duty to allow people to enjoy the peace and tranquility on the island - those two things are in conflict with each other - it's a case of getting those two things in balance."
Seals, choughs and shearwaters share the island with eight residents, including farmers David and Libby Barnden, whose first year was portrayed in the BBC documentary Love on a Rock.
Welsh Black cattle and sheep graze in the fields beside the bird observatory, lighthouse, chapel, medieval abbey ruins and the stone Victorian farmhouses that provide accommodation for summer visitors.
Visitors to the Island travel there from Pwllheli or Porth Meudwy, near Aberdaron, over rough seas called the "swnt" throughout the summer months.
The BBC Wales Welsh-language current affairs programme Taro Naw will be on S4C on Wednesday, 17 September at 2025 BST.