The broadcaster Chris Packham has said he will continue his fight against the construction of HS2, which environmentalists say is leading to irreversible destruction of ancient habitats and woodlands.

Last week Packham applied for an urgent injunction to halt construction work and argued for a judicial review of the government’s decision-making process in relation to the £106bn high-speed railway.

The high court dismissed his case, concluding: “The clearance works were long ago authorised by parliament and there is a strong public interest in ensuring that, in a democracy, activities sanctioned by parliament are not stopped by individuals merely because they do not personally agree with them.”

On Saturday Packham said he would appeal against the decision. “In these times of climate and environmental emergency, resilience is key,” he said. “Now is not the time to give up, now is the time to muster and protect what we have left.”

He said he was heartbroken at the failure to halt the ongoing clearance works on the project and said ancient trees and important habitats were being lost.

“These are ancient woodlands that used to provide a safe and stable home to an abundance of wildlife, parts of which are now gone forever,” he said. “The works are completely irreversible. Yet still we fight on, as we must try to protect all the other precious flora and fauna which is at risk from the HS2 project.”

A number of MPs wrote to HS2 Ltd’s chief executive, Mark Thurston, last month detailing residents’ concerns about the project and urging him to halt all construction work during the coronavirus emergency.

There have been claims that construction teams were ignoring the government’s physical distancing rules during the lockdown.

The RSPB has also urged HS2 not to clear woods during the April–September nesting season. Destruction of active birds’ nests is illegal, and the charity has asked local people to report any incidents they see to the police.

Five ancient woodlands are the focus of HS2 “enabling” works: Broadwells Wood, Birches Wood, Crackley Woods and Ashow Road Wood in Warwickshire and Fulfen Wood in Staffordshire.

Packham had been seeking an interim injunction from the high court to halt all clearance and construction works. He was also seeking a judicial review of the decision to allow HS2 to proceed, on the basis that it was predicated on the findings and recommendations of the Oakervee review. Packham said the review – by a former chair of HS2 Ltd – failed to provide an independent, impartial and rigorous appraisal of relevant environmental and climate change factors.

Carol Day, a solicitor at the law firm Leigh Day, which is representing Packham, argued that the high court had failed to “properly address parts of his claim in relation to the loss of irreplaceable ancient woodlands and climate change”.

She added: “He [Packham] believes that if the government is determined to proceed with this costly and damaging project, it must be on the basis of a full and proper understanding of the environmental impacts. Now more than ever it should be recognised that meeting our international environmental obligations has a vital part to play in protecting nature and human health.”

A spokesperson for HS2 said all its ecology work was carried out in accordance with the law under the supervision of professionally qualified ecologists. It said licences from Natural England ensured the correct safeguards were in place to protect wildlife.

Its statement added: “To ensure the health, safety and wellbeing of our workforce and the communities in which we are working, only construction sites that can maintain government guidelines and are critical to the delivery of HS2 will remain operational.”

It said work had paused at some sites, “although some sites may remobilise if our contractors are confident they can operate in line with PHE and industry guidance”.

It said: “Those sites still working are doing so because they are confident they are operating within PHE guidelines, and will be monitored and remain under constant review.”

A DfT spokesperson said: “We have tasked HS2 Ltd with delivering one of the UK’s most environmentally responsible infrastructure projects. While our current priority is combating the spread of coronavirus, we must continue our work to level up the country. HS2 will be crucial to that ambition, boosting capacity and connectivity across our rail network.”