It would surely have been a first. A councillor sent to prison because the council they sit on didn’t just bring its own legal action against them, it called for a custodial sentence.

Alison Teal, a Green councillor in Sheffield, has long opposed the council's plan to fell thousands of roadside trees. On this occasion, she was accused of breaching an earlier court injunction, which forbade people from entering "safety zones" the council has set up around trees it wants to fell. Teal said she had been "fastidious" in respecting the terms of the injunction.

On Friday, a judge threw out Sheffield council’s case against her. But the authoritarian and heavy-handed approach of the Labour majority council is symptomatic of a problem that is widespread across England.

Where I live in Lambeth, south London, there are 58 Labour councillors and an opposition of just four – five if you include the Labour councillor who has gone independent because she feels the ruling party is riding roughshod over the wishes of local people.

Estates like Cressingham Gardens in Tulse Hill and Central Hill near Crystal Palace are to be bulldozed against residents' wishes – despite a promise by the council leader to do nothing against the residents' wishes. And despite the fact that residents came up with their own alternative plans that would have created more truly affordable homes for local people.

But it isn’t just that residents' voices are being ignored. An enquiry by Lambeth Green Party councillor Scott Ainslie revealed that the council had made a staggering £56m from the eviction of residents and destruction and sale of housing co-ops. Yet in 10 years, it has built only three new council homes. The council's energy seems to be focused on closing libraries, and pushing ahead with precisely the programme of gentrification and social cleansing that Jeremy Corbyn condemned in his speech to the Labour party conference in September.

This is what happens when a council becomes all powerful. And it is often Green party councillors like Ainslie in Lambeth, or Teal in Sheffield, who are the sole voice of opposition against the complacency and destruction of these councils that have lost touch with local people. And those voices are so important. For while there may be a growing opposition against misguided and destructive government policies like Universal Credit at the national level, at the local level both Labour and Conservative councils are failing to ring fence former Independent Living Fund money for the disabled.

As more and more people raise concerns about air pollution and climate change, councils are ploughing on unchecked with waste incineration. Others are increasingly calling in the bailiffs against those who fall into debt after cuts to their council tax support.

As in my own situation in Lambeth – where Greens came second in the last council elections – it’s not uncommon to have a one-party state. The first-past-the-post voting system is as undemocratic and distorting at the local level as it is at Westminster. In the cases of Lewisham and Islington, Greens are the sole opposition. One seat separating the people of those boroughs from living under a total majority of Labour councillors, no matter who they voted for.

Like many Green councillors, Teal stood for office because she wanted to make a difference in her community. She was hesitant. But at the last minute, with the deadline approaching, friends in her local party talked her into it.

It’s fair to say she hasn’t looked back since. She’s an inspiration. Her work for residents in Sheffield has seen her be the recipient not only of a Green Party award of recognition but also made her a nominee for the Local Government Association’s Councillor of the Year award.

Like many Green councillors she was prepared to tell it like it is, and shine a light on what the council was doing. But when she started out, she can’t have imagined then what she would have been subjected to. There has been a huge cost, because councils like Lambeth and Sheffield hate being challenged and scrutinised.

For several years, Teal had, along with her fellow members of the Sheffield Tree Action Group (Stag), been protesting the move by her Labour colleagues to fell hundreds of trees in the city. During that time, it became clear the council's priority was saving money, rather than taking wider residents' concerns into account. The majority of residents do not support what their council is doing, and that’s according to the authority’s own much-maligned survey.

The response from the council to the dissent of Teal and her allies in Stag has been outrageous. Rather than listening to their concerns, rather than trying to understand why Sheffield residents might be concerned to see ancient trees disappearing from outside their own homes, they tried to shut her up.

Alison was in court on Friday because the council believed she had breached a court order aimed at denying her right to protest against felling. She hadn’t. The judge saw that and threw the case out within a few hours. But it shows how loud one opposition voice can be.

Everywhere across Britain we need more Alisons. That’s why I’ve decided to stand myself in 2018 in Lambeth – and why I’m encouraging Greens across the country to do the same. The dominance of individual political parties on councils is not a reason to give up the fight – it’s a reason to fight even harder.