A public inquiry into long-awaited plans to widen one of the county's busiest stretches of road gets under way today.

Supporters of the scheme to widen a 2.5mile stretch of the A21 between Tonbridge and Pembury hope the 12-day inquiry will mark a major step forward for a scheme dogged by uncertainty and delays for more than a decade.

The scheme, costing between an estimated £100m and £150m, has been on the cards for some time, but was a victim of the government's public sector spending squeeze.

Last May, the transport minister Mike Penning announced the inquiry would go ahead and he wanted the scheme to get the green light but it was unlikely to do so before 2015.

The inquiry at the Mercure Hotel in Tunbridge Wells will take evidence from both supporters and opponents.

Highways Agency project manager Graham Link said: "This inquiry is an important step for the delivery of this much-needed upgrade to the A21.

"All views will be considered, and I look forward to helping to present the agency's case for these improvements."

The scheme aims to ease congestion on a stretch of road carrying 40,000 vehicles a day and improve journey times to Pembury Hospital.

While the widening scheme has been welcomed by many motorists, not everyone is happy.

The Woodland Trust said it would put nine hectares of ancient woodland at risk, along with the wildlife that depends on it for survival.

The Woodland Trust's head of campaigning, Nikki Williams, said: "This ancient woodland is easily comparable to a Site of Special Scientific Interest due to its range of fungi.

"The Environmental Impact Assessment for the project itself states that 'most of the woodland adjacent to the A21 is designated for its nature conservation value.

"Wildlife found in the woods include more than 1,000 species of fungi - some so rare they do not have common names, plus invertebrates such as glow worms, 10 species of ladybird, 24 species of bee and at least 13 species of butterfly."