The Green Party has dropped its historic opposition to HS2, with party members backing the change in position at the party conference.

The motion, which won the backing of a majority of Greens at the Manchester conference, means the party now officially supports the full high-speed rail project.

This includes the two northern sections of the route that the Conservatives have abandoned, stretching from Birmingham to Leeds and Manchester, where the party wants to build a terminus for the underground railway.

The move could put pressure on Sir Keir Starmer’s government to consider reactivating the northern sections of HS2 and prevent the Greens from winning over Labour voters.

The Green Party came second in 40 constituencies, all but one of which went to Labour, suggesting that a clash with Sir Keir’s party could be the route to future success.

Green Party co-leader Carla Denyer, who was unable to address the conference because she developed COVID-19-like symptoms, welcomed the motion.

She said: “The Green Party has long supported the idea of ​​a new north-south high-speed rail line, but has serious concerns about the specific route of HS2 and its impact on the environment.

“But this first phase of HS2 between London and Birmingham is already underway and most of the environmental impacts of construction have been addressed. So this is a pragmatic decision by the Green Party. It moves us forward.”

She added that the northern section of the project “has always been the most important in terms of solving the capacity challenges facing our railways.”

The other Green Party co-leader, Adrian Ramsay, signalled support for the policy change ahead of the vote, which took place on the final day of the party conference.

He told the PA news agency there was “a case” for HS2 to be fully built, but added that official policy was a matter for party members.

The Greens have in the past criticised the environmental damage caused by the London to Birmingham section of HS2 and opposed the project when it got underway.