Michael Meacher, who died yesterday after a short illness, was a remarkable environment minister.

For six years, at the start of the Blair government, he almost single-handedly fought to defend the natural world from road-building, the first generation of GM crops and rampant industrialisation.

While junior environment ministers usually accept the Treasury or No 10 line without question, ‘the Meach’, as he was widely known, stood up to Tony Blair and Gordon Brown – and possibly saved the administration from political embarrassment by urging caution at key moments.

His first task was to extricate Blair from the potential embarrassment of introducing GM crops. Blair had been persuaded by David Sainsbury, the head of a large food multinational, that GM crops were the future and posed no danger to consumers.

But with public opinion strongly against them, Meacher defused the debate by negotiating a three-year moratorium during which further tests were done. By pleading caution, he gained the trust of both hostile environment groups and wary consumers.

Not popular at Number 10 – but somehow, he held on

He was widely disliked in No 10 and was denied a cabinet position, but he survived in the environment job possibly because Blair feared that he would be a dangerous backbencher with scientific credibility.

My colleague, the environment correspondent Paul Brown, wrote in 2002: “The prime minister’s impatience with Michael Meacher, the only minister who urges caution and is seen by No 10 to stand in his way, became public when Mr Blair tried to drop his environment minister from the team attending the Earth summit in Johannesburg in 2002.

“After public protest John Prescott, the deputy prime minister, reinstated him – but it was not the first time Mr Meacher and Mr Blair had crossed swords.

“During the mini-reshuffle brought about by the resignation of Stephen Byers from transport, Mr Blair tried to push Mr Meacher into a less high profile post. It is said that Mr Meacher threatened to resign from the government altogether rather than be moved.”

When he finally left government in 2003, Meacher became a strong voice for environment protection, urging government and personal action on climate change, which he grasped as the most important long-term issue of the time.

What a legacy: the ‘right to roam law’

But he will be remembered especially for steering through the ‘right to roam‘ legislation, which surprised and delighted ramblers and Labour backbenchers even as it infuriated landowners by promising a statutory right of access to 1.6m hectares (4m acres) of open countryside in England and Wales.

The commitment, which was explicitly linked by Meacher to the memory of the late Labour leader and keen fellwalker John Smith, reassured many Labour MPs who had feared Blair would be swayed by pressure from the powerful countryside lobby to abandon a principle close to party’s heart since its inception.

And he remained a radical, campaigning MP to the end, supporting the Occupy Democracy gathering in Parliament Square in October 2014 (see photo). Retaining his Oldham West and Royton in the 2015 election with a 14,738 majority he was one of the few Labour MPs to support Jeremy Corbyn in the leadership contest.

He described Corbyn’s election as a “seminal day in British politics, marking the coming together of the two great conditions needed for transformational change.” As a backbencher, Meacher wrote almost daily blogposts about the politics of the day, often making the case for anti-austerity economics.

Gordon Brown, the former prime minister, yesterday praised his contribution to Britain’s political life: “The Michael I have known for more than 30 years was a man was a prodigious writer, a talented speaker, a reforming minister and highly effective propagandist who with little thought for his own health campaigned relentlessly for social justice and for a fairer Britain throughout his life.

“His deeply held commitment to ending poverty marked him out as a tribune of the people and his always thoughtful contributions to debates on the environment, economy and social policy will be sorely missed.”

John Vidal is the Guardian’s environment editor.

This article was originally published on the Guardian and is republished with thanks via the Guardian Environment Network.