Right to roam laws have prompted a revamp of OS maps

The Ordnance Survey (OS) explorer map, the standard walkers' guide, currently shows national park boundaries such as Dartmoor and Exmoor in bright yellow.

But the OS plans to remove any sign of the boundary in the new series.

Ramblers and park authorities have reacted angrily, calling the move "ludicrous" and "ridiculous".

The OS said the change was necessary because of new right to roam access rights, which required much more information on maps.

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Leaving the parks boundary out stopped the maps becoming cluttered and confusing.

The OS also pointed out that the maps were a draft, a final decision would be made in May, and the boundaries would be marked on other maps.

Spokesman Scott Sinclair said: "We have done a lot of consultation and they key point is that the maps have to be clear.

"We need to avoid any misunderstandings between users of the countryside and landowners."

Approved maps of the UK will be completed in 2005 when the right to roam access rights will be granted.

Dartmoor National Park authority called the new maps "ludicrous".

It is absolutely essential that national park boundaries are shown on Ordnance Survey maps Don Millgate, Ramblers Association

Jeff Haynes of the Dartmoor National Park Authority, said: "We think it's a bizarre suggestion to take the national park boundary off the explorer map.

"They are the one of the most important maps for walkers and we think it is a ludicrous proposal."

Exmoor National Park called the move "extraordinary" and said they were "disappointed" by the change.

The Ramblers Association said that knowing the boundaries was important as they marked the beginning of some legal rights of access, and for dog walking and horse riding.

Spokesman Don Millgate said: "It seems absurd to us.

"It is absolutely essential that national park boundaries are shown on Ordnance Survey maps."

The right to roam plans have already faced fierce resistance from some farmers reluctant to open up their land to the public.

They believe many people have no respect for the country code and that opening up routes under the Countryside and Rights of Way Act 2000 will leave them with damage to property and livestock.

They are particularly worried about people allowing their dogs off the lead while walking on farmland.