The Millennium Seed Bank is facing a funding shortfall that could force it to halt operations.

Scientists at the seed bank need to raise more than £100 million in little more than a year to safeguard the facility’s future. Failure to secure the money would put the survival of hundreds of species of plant at risk and damage Britain’s credibility as a centre of scientific excellence.

Kew’s Millennium Seed Bank was opened to a fanfare of acclaim in 2000 with the aim of being the plant world’s ark by gathering seeds from every flowering plant on the planet and keeping them safely in cold storage.

It has enough cash to keep it open until the end of 2009 but managers have been unable to secure adequate funding for 2010 or beyond. More than £100 million is needed for the seed bank to have a chance of reaching its 2020 target but less than a fifth has been offered.

Paul Smith, the head of the seed bank, fears that the banking crisis will only exacerbate the difficulty of raising enough funds to keep the seed bank operating after 2009. He said: “We are running out of time. We are staring down the barrel of a gun. We have enough to maintain things as they are but we have the vast majority of the funding still to raise. If we can’t get it our hopes of collecting seeds from the many plants under threat – the purpose for which the seed bank was built – will disappear.”

By the end of next year staff at the seed bank, based in Wakehurst Place, West Sussex, part of Royal Botanic Gardens Kew, expect to have collected seeds from 24,200 species, 10 per cent of the estimated world total in 2000. The second phase of the seed project is to collect seeds from a further 15 per cent of flowering plant species, to ensure that by 2020 a quarter of the world’s total are stored safely.

Failure to secure sufficient money for phase two means the conservation work of collecting more seeds from plants around the world could be halted well before 2020. A skeleton staff would be kept to ensure that the freezers where the seeds are stored at minus 20C (-4F) were kept working but little more would be achieved.

Seeds already stored at Wakehurst Place include at least six species of plant that are believed to have died out in the wild. Three vanished after plant experts collected seeds for the seed bank, the other three had already died out by 2000 but a handful of seeds were passed to the Wakehurst facility by collectors for safekeeping.

Negotiations have taken place with Defra and other government departments but all are under pressure to keep costs down, especially Defra, which suffered budget cuts last year.

One of the chief concerns is that without significantly more money the team of specialist researchers, who have won an international reputation for excellence for their work, will disperse to more secure institutions.

So worried are senior figures at Kew that they have put together a team to lobby government departments, funding bodies and wealthy people.

Dr Smith added: “We need stability. We can always scale up or scale down but the first thing we have to do is secure skills here. It will be a disaster if it shuts. We will lose significant numbers of plant species.”

Another significant element of the unit’s work that would be lost without sufficient money is the training of botanists from other countries, particularly developing nations.

Ten per cent of all flowering plants around the world are threatened and by ensuring their seeds survive they can be saved for future generations. More can be grown if the species die out in the wild or become so rare as to be unviable in the long term Professor Hugh Pritchard, head of conservation at the Millennium Seed Bank Project, said that with plants already dying out the seed bank’s task becomes more urgent with each year.

Such is the impact of mankind’s activities on the planet that researchers estimate at least four species of plant vanish every year.

Professor Pritchard said: “There is no other programme like this. With the shifts in habitat caused by climate change it becomes increasingly important to get plants quickly.”

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