Built with Fort Knox-type security, the $3 million vault will be designed to hold around two million seeds representing all known varieties of the world's crops.

They are the precious food plants that have emerged from 10,000 years of selection by farmers.

The facility "would essentially be built to last forever," according to a feasibility study.

It will be built deep in permafrost in the side of a sandstone mountain on the Norwegian island of Spitsbergen, 1000km from the North Pole, the British weekly says in its next issue, out on Saturday.

With walls of one-metre-thick concrete, the seed bank will be protected behind two airlocks and high-security blast-proof doors.

Freezing point

The facility will not be permanently manned but "the mountains are patrolled by polar bears", the report quotes Cary Fowler, director of the Global Crop Diversity Trust, an organisation that is promoting the project, as saying.

Norway floated a similar proposal
unsuccessfully in the 1980s

To be preserved, the seeds must be kept below freezing point. Operators plan to replace the air inside the vault once a year at winter-time, but even if for some reason this becomes impossible, the permafrost will still keep the seeds viable.

The thick walls, airlocks and doors mean that even if global warming accelerates badly, it would take many decades for hotter air to reach the seeds.

"This will be the world's most secure gene bank by some orders of magnitude," said Fowler. "But its seeds will only be used when all other samples have gone for some reason. It is a fail-safe depository, rather than a conventional seed bank."

The proposal is backed by Norway, which sketched a similar project back in the 1980s that was thwarted at the time by the Soviet Union's access to Spitsbergen.

The seed bank is expected to be created next year, New Scientist says.