British Nuclear Fuels insists the conclusions reached by the environmental pressure group are based on misleading and selective interpretation of data.

But Greenpeace say their research compared soil samples from the Cumbrian and Ukranian plants and proved Sellafield has the higher levels.

A 30km exclusion zone has remained in place around Chernobyl since the disaster there in 1986.

Chernobyl: Scene of the world's worst nuclear accident

Greenpeace says this area, where people and agriculture are banned, is safer than the comparable region around Sellafield.

Samples were taken from comparable distances around the two nuclear power stations and then examined, it says.

Some contamination levels were comparable, while others were higher in the Sellafield area.

Greenpeace says 23 times the level of Americium-241 - a highly radioactive, carcinogenic substance - was found at Sellafield compared to Chernobyl.

Greenpeace campaigner Dr Helen Wallace said: "Sellafield is a slow-motion Chernobyl, an accident played out over the last four decades.

"If the government cares about the people it represents it must stop radioactive discharges from Sellafield immediately by ending the dirty, polluting practice of nuclear reprocessing."

But BNFL dismissed the claims as "scaremongering, using some selective information in order to try to mislead the public on Sellafield and its effect on the environment".