Britain has approved a controversial plan to build a road tunnel close to the prehistoric site of Stonehenge to relieve congestion, despite strong opposition from archaeologists and druids.

The 5,000-year-old ring of stones in Wiltshire in southwest England is a UNESCO World Heritage site and one of Britain's most popular tourist attractions, with 1.6 million visitors last year.

Transport Secretary Grant Shapps on Thursday approved a plan to bore a tunnel to replace a busy road that passes within 165 metres of the stones, allowing drivers to see the site but making it a noisy experience for visitors.

Tom Holland, the head of the Stonehenge Alliance which includes archaeologists and non-governmental organisations, condemned what he called a "shocking and shameful decision".

The writer said the tunnel would "inject a great gash of concrete and tarmac into Britain's most precious prehistoric landscape".

Opponents criticise the fact that while the tunnel won't go directly under the stones, its entrances will be built within the broader World Heritage Site which could damage prehistoric areas.

They say that if built, the tunnel should be much longer.

Druids, who have held protests against the tunnel, and neopagans celebrate the festival of 'Winter Solstice' every December 21. Photo: Ben Stansall/AFP

Druids have held protests against the tunnel at a site they consider sacred and where they celebrate the summer and winter solstice – the longest and shortest days of the year.

But English Heritage, the charity that manages the Neolithic site, hailed a "landmark" decision, tweeting that "Stonehenge will finally be reconnected with the prehistoric landscape in wich it sits" without a noisy road nearby.

Officials say the existing road is too narrow for the current level of traffic, with the government roads agency, Highways England, calling it a "daily struggle for many”.

The tunnel will be around 3.2 kilometres long. At its closest point, it will be 200 metres from Stonehenge, slightly further than the current road, Highways England said.

The government first approved the plan in 2017. Its budget is now given as £1.7 billion (€1.9 billion).

Stonehenge is currently closed to visitors due to coronavirus restrictions across England.

Work is expected to start next year, Highways England said. It said it had appointed archaeology specialists to excavate the site and preserve any finds.