This is how it begins: with a theatrical attack on a vulnerable minority. It’s a Conservative tradition, during election campaigns, to vilify Romany Gypsies and Travellers: it tends to play well on the doorsteps of middle England. But what the home secretary, Priti Patel, proposed last week is something else. It amounts to legislative cleansing.

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The consultation document she released on the last day of parliament aims to “test the appetite to go further” than any previous laws. It suggests that the police should be able immediately to confiscate the vehicles of “anyone whom they suspect to be trespassing on land with the purpose of residing on it”. Until successive Conservative governments began working on it, trespass was a civil and trivial matter. Now it is treated as a crime so serious that on mere suspicion you can lose your home.

When I say “you”, obviously I don’t mean you, unless you are a Romany Gypsy, a traditional Traveller or a New Traveller. If you’re on holiday in your caravan, it does not affect you. It applies only if you have “intent to reside” in your vehicle “for any period”. In other words, it is specifically aimed at travelling peoples. It is clearly and deliberately discriminatory.

It’s true that some people have sometimes behaved appallingly, damaging places, leaving litter and abusing residents. But there are already plenty of laws to prosecute these crimes. The government’s proposal, criminalising the use of any place without planning permission for Roma and Travellers to stop, would extinguish the travelling life.

The consultation acknowledges that there is nowhere else for these communities to go, other than the council house waiting list, which means abandoning the key elements of their culture. During the Conservative purge in the late 1980s and early 1990s, two thirds of traditional, informal stopping sites for travellers, some of which had been in use for thousands of years, were sealed off. Then, in 1994, the Criminal Justice Act repealed the duty of local authorities to provide official sites for Roma and Travellers.

Facebook Twitter Pinterest ‘Priti Patel is beating up a marginalised group in full public view, to show that she sides with the majority.’ Photograph: Wiktor Szymanowicz/Barcroft Media

Over the past few weeks in Grimsby, Lincolnshire, local people have been debating the merits of the council’s proposal for an official transit site for travelling people. According to one councillor, there have been threats to stone, bottle and petrol bomb anyone who uses it, if planning permission is granted. For centuries, Roma and Travellers have been hounded from parish to parish, suffering prejudice and bigotry as extreme as any group faces. Now the government is stoking it.

Patel’s proposed laws belong to the most dangerous of all political categories: performative oppression. She is beating up a marginalised group in full public view, to show that she sides with the majority. I don’t know whether she really intends to introduce these laws, or whether this is empty electioneering. In either case, she is playing with fire. Already this month, three caravans in Somerset have allegedly been torched by suspected arsonists. Travelling peoples have been attacked like this for centuries, and sometimes murdered. In 2003, a 15-year-old Traveller child, Johnny Delaney, was kicked to death by a gang of teenagers in Ellesmere Port, Cheshire. One of them is reported to have explained to a passer-by, “He was only a fucking Gypsy.”

I asked a traditional Traveller how Patel’s legislation would affect her. Briony (not her real name) told me she had ploughed her life savings into her motorhome, which she parks out of people’s way, beside roads within easy reach of her children’s school. She has good relations with local people, many of whom know her and see her as part of the community. But none of this will help.

If this proposal becomes law, “the police will have the power to kick my door in, take my home, arrest me and take the children into care. We won’t get them back because we won’t have a home. Because of my work, I can’t afford a criminal record. When I walk out of the police station, I will have no home, no assets, no children and no career.” It would also leave her without state protection. “Sometimes, we’ve had to call the police when we’re on the receiving end of hate crimes. This legislation would mean we had to go under the radar.” Understandably, she is terrified.

She has nowhere else to go. “There’s one transit site half an hour away, but you can stay there only for 28 days a year. So my only option is roadside. Roadside is our cultural heritage.” Stopping by the road has already been made extremely stressful and precarious by existing laws that allow the police to move people on. Patel’s proposal, turning trespass into a crime, would stamp it out altogether. It would end a migratory tradition that’s as old as humanity.

As Briony points out, this is collective punishment. “The majority of us are minding our own business. We’re providing our own housing, not relying on the government. But everything I do that’s positive is lost in people’s minds. Most people I meet have no idea I’m a Traveller. We’re invisible until we do something wrong. Then people notice we’re Travellers.”

A week before Patel launched her consultation, the Wiener Holocaust Library in London opened its exhibition on the Porajmos: the genocide of Roma and Sinti people carried out by the Nazis. It shows how ancient prejudices were mobilised to destroy entire peoples. I’m not saying that this is how the situation will unfold in this country, but the exhibition shows us the worst that can happen when the state sanctions the demonisation of an outgroup. First they came for the Travellers …

• George Monbiot is a Guardian columnist