The trust says 10 tankers would carry one million tonnes of oil
Conservationists have said oil tankers anchored off the Jurassic Coast are an "accident waiting to happen" and have called for them to be moved.
The vessels are in Lyme Bay, on the Dorset-Devon border, which forms part of a World Heritage site.
But Dorset Wildlife trust said that with storms and gale force winds setting in, the ships should be moved to more sheltered harbours.
The Environment Agency says the issue is "not within its remit".
The number of tankers in the bay varies but up to 10 have been recorded.
The Dorset Wildlife Trust said the tankers could be carrying up to one million tonnes of crude oil.
The ships are thought to be anchored while the owners wait for oil prices to rise.
Trust chief executive Simon Cripps said: "This is an accident waiting to happen.
"Even a minor spill or accident would devastate one of the world's most valuable and sensitive coasts, killing animals and plants and ruining livelihoods for years.
"This is not a nimby [not in my back yard] approach. This is common sense risk management.
"It is a very silly place to park a million tonnes of oil.
"You [should] put them in ports where they can be safely contained if there's any spillage and where the weather can be better managed.
"We would like to see regulations to prevent them from threatening such important areas in the future."
Mr Cripps said the vessels' safety standards were "unclear".
It was not known, he said, whether the ships were single or double hulled or how securely they were anchored.
Lyme Bay is an important conservation area and is covered by special laws to protect reefs by banning bottom trawling in parts of the bay.
The bay is an important angling, fishing and tourism area.
Oliver Letwin, MP for West Dorset, said: "I think the problem here is one of safety.
"I have no idea who exactly is hoping to make what kind of money out of which kind of manoeuvre.
"But what I'm very clear about is that we really can't have enormously large oil tankers sitting off an incredibly environmentally sensitive coast for an indefinite period."
Mr Letwin said he had written to the secretary of state for transport to ask for a full account of what ships are in Lyme Bay and why, how long they will be allowed to stay and what safety procedures are in place.
A spokesman for the Environment Agency said tankers have been stopping in Lyme Bay for various reasons for more than 30 years.
"It is a natural sheltered bay where they stop, often in large numbers," he said.
"Clearly, there are emergency procedures in place but it would be for the local authority to respond to an oil spillage so it's not in our remit to comment."