Human rights campaigners have begun legal action against the home secretary, Suella Braverman, after she forced draconian new police powers through parliament in a move described by the House of Lords as a “constitutional outrage”. Liberty wrote to Braverman on Wednesday, saying her move to empower police to curtail or restrict protests that caused “more than minor” disruption was unlawful. This week the government used secondary legislation, which is subject to less parliamentary scrutiny, to grant police the power. An attempt to include it as a late amendment to the recent Public Order Act 2023 failed to pass the Lords in January. Braverman told MPs on Wednesday the new powers would enable police to take quicker action against slow-walking protests and those that brought “chaos to the law-abiding majority”. But in its pre-action letter, the first step to a judicial review, Liberty said her move violated the constitutional principle of the separation of powers, because the measures had already been rejected by parliament. Katy Watts, a lawyer for the human rights organisation, said: “The home secretary has sidelined parliament to sneak in new legislation via the back door, despite not having the powers to do so. “This has been done deliberately in a way which enables the government to circumvent parliament – who voted these same proposals down just a few months ago – and is a flagrant breach of the separation of powers that exist in our constitution. “We’ve launched this legal action to ensure this overreach is checked, and that the government is not allowed to put itself above the law to do whatever it wants. It’s really important the government respects the law and that today’s decision is reversed immediately.” The Home Office confirmed it had received Liberty’s letter. A spokesperson said: “The right to protest is a fundamental part of our democracy but we must also protect the law-abiding majority’s right to go about their daily lives. That is why have introduced a new definition of serious disruption, to give police the confidence they need to clear roads quickly. The was voted on by both the House of Commons and House of Lords, following proper parliamentary procedure.” The regulations, a response to daily roads protests by climate activists, lower the threshold for what constitutes “serious disruption” to the public from “significant” and “prolonged” to “more than minor”. One legal expert has suggested the change will give police “near total discretion” over which protests to allow and which to curtail. Liberty says the regulations now give police “almost unlimited powers” to stop protests Braverman said on Monday that the public had “lost their patience” with Just Stop Oil, the climate activist group that has staged 156 slow marches in London in the past six weeks. “The police must be able to stop this happening and it’s our job in government to give them the powers to do so,” she told the Commons as it passed the measure. But the use of secondary legislation to push through a rejected proposal has prompted accusations that the government is flouting democracy by playing fast and loose with constitutional laws. A cross-party committee of peers recently said it was the first time a government had tried such a move. Secondary legislation is law created by ministers under powers given to them by acts of parliament. It is used to fill in the details of acts, so they can be swiftly adapted to changing circumstances. But increasing use of secondary legislation to fill in so-called “skeleton bills” has led to concerns of a shift in power towards the executive. On Tuesday night, peers accused the Home Office of authoritarian and disreputable behaviour as they backed, by 177 votes to 141, a so-called regret motion proposed by Labour that criticised the process and urged the withdrawal of the provisions. Vernon Coaker, Labour’s home affairs spokesperson in the Lords, said: “It is an absolute fundamental constitutional outrage, what has actually taken place. Primary legislation was defeated. So what does the government do? It doesn’t bring forward new primary legislation; it tries to sneak through, in an underhand way, secondary legislation without proper public consultation. They undermine the workings of our parliamentary democracy and, as such, it is shocking.” A rare fatal motion brought by Jenny Jones of the Green party that aimed to kill off the regulations was defeated by 154 to 68. Labour had refused to back it, despite calls from Lady Jones and a 64,000-strong petition. The crossbench peer David Pannick KC also called the government’s move a constitutional outrage. The leading constitutional lawyer added: “All we can do … is express regret: we are very sorry about this. “Well, I express regret that the Labour frontbench is not prepared to see through the implications of its own view that this is a constitutional outrage. It is something that we should stand up against and vote against.”