A new disease killing native oak trees could alter the British landscape even more than Dutch elm disease, woodland groups warned yesterday as they called for more funding to tackle the problem.

Acute oak decline is hitting both species of native oak, which show black bleeding on the trunk and stems and can suffer rapid dieback and death within three to five years, experts said.

The disease hitting the country's "iconic" tree has been found on 55 sites in the east of England, southern England and the Midlands, and experts warn other suspect cases have yet to be confirmed.

Woodland charities and commercial forestry groups are calling for £10 million over the next five years to investigate tree diseases - with acute oak decline a priority for research.

Peter Goodwin, of Woodland Heritage, said: "We're looking at a disease that has the potential to change our landscape even more than Dutch elm disease, and nothing is being done about it.

"We can't afford a repetition of what happened then. Action is needed now."

Hilary Allison, policy director at the Woodland Trust, said the loss of such an iconic tree from the landscape would be "catastrophic".

The Woodland Trust has one site, Hoddesdon Park Wood in Hertfordshire, where the disease has been confirmed, and five more suspected cases elsewhere in the country.

Andy Sharkey, the trust's head of woodland management, said research is needed to find out more about the condition, how it is spreading and what could be done to prevent or minimise its impacts.

Forest Research, the research arm of the Forestry Commission, has identified a bacterium which appears to be entirely new to science in the trees with the disease.

But Mr Sharkey said it is not clear if the bacterial infection is the primary cause of the disease, or a final stage of the condition.

He also said more research is needed to find out the extent of the disease, as the 55 confirmed sites have all been reported by landowners or managers and no systematic survey of oak woods has been done.

He said the disease, which affects sessile and pedunculate oaks, is of such concern because of the speed with which it is damaging the trees which make up most of our woodlands.

"This is our most iconic tree, it totally dominates our landscape, and here we have a potentially new disease that leads to rapid decline of the tree.

"We need to know more about it, that's why we're concerned and that's why we're making that call."

He added: "If it's as bad as we feel it could be we need to understand and get to grips with it now."

Currently landowners and woodland managers have little idea about how to deal with the problem - including whether to fell the infected trees, he said.

The groups supporting the call for the incoming government to allocate more funds to Forest Research to investigate tree diseases include the Royal Forestry Society, the Woodland Trust, Woodland Heritage, the Tree Council, Institute of Chartered Foresters, Arboricultural Association, Confederation of Forest Industries and the Country Land and Business Association.