The broadcaster Chris Packham has lost his case against HS2 in the court of appeal.
Environmentalists say the high-speed rail project is leading to irreversible destruction of ancient habitats and woodlands.
Packham said the case for HS2 should be revisited despite Friday’s ruling against him.
The judgment refused permission on two grounds for a judicial review into the cabinet’s decision to give the multibillion pound project the “green signal” in February.
Packham believes the Covid-19 pandemic’s impact on public finances and the need for a green recovery has undone the business and environmental case for HS2.
“Obviously we are deeply disappointed by today’s ruling. But the fact is, we are a world away from the place we were when we issued the original claim for judicial review,” he said.
“Covid-19 has turned the state of the UK finances and the public’s attitudes towards climate change upside down. People now see that a scheme for a railway which will tear up the countryside so that we can shave a few minutes off a journey time makes no sense in the contemporary workplace.”
The first of Packham’s two grounds of appeal concerned the question of whether the cabinet was correctly advised on the existence and extent of environmental information before it when considering the report of the Oakervee review.
The second was that the government failed to take account of the effect of the project on greenhouse gas emissions and global temperature rise between now and 2050, in the light of its obligations under the Paris agreement and the Climate Change Act 2008.
On the first ground, the judges ruled that the environmental impacts of HS2 had been assessed in detail through the parliamentary process and the cabinet’s decision-making could not have been made without proper regard to those conclusions.
On the second, the court held that because the decision arising out of the Oakervee review was not subject to any form of statutory scheme, the government was at liberty to select the issues on which it was advised by the review and that it was not constrained by the act or by any policy of its own.
The court held that it can be taken that the government was fully aware of its commitments under the Paris agreement and responsibilities under the act and to have taken those commitments and responsibilities into account.
Packham’s solicitor, Carol Day of Leigh Day solicitors, said: “This is a very disappointing judgment. Most people would assume that when the government makes a commitment to tackle climate change under international and domestic law, that commitment will be both fully understood and fully considered in all of its decision-making.
“However, today’s judgment suggests a less demanding approach can be lawful. Our client believes this is wrong and is pursuing the possibility of an appeal.”
A spokesperson for HS2 Ltd said: “From the outset HS2 Ltd has taken our commitment to the environment extremely seriously. The act of parliament gives us the legitimacy to carry out work to build the railway, and licenses from Natural England and approvals from the Environment Agency ensure that we have the right safeguarding in place to protect wildlife and other natural assets.
“All leading environment organisations agree that climate change is the biggest future threat to wildlife and habitats in the UK. By providing a cleaner, greener way to travel, HS2 will help cut the number of cars and lorries on our roads, cut demand for domestic flights, and help get Britain to net zero carbon emissions.
“Today is a good day for the long term future of Britain’s natural environment.”