LONDON — British Prime Minister Theresa May has vowed to toughen anti-terrorism laws following last weekend’s attacks in London, but she could face opposition because of public concern for civil liberties and other laws protecting human rights.

Britain already has a long roster of security tools, headed by so-called Terrorism Prevention and Investigation Measures, or TPims, but some experts have criticised them as being not strict enough.

Introduced in 2012 and toughened in 2015, TPims apply to people who are deemed a threat but cannot be prosecuted or, in the case of foreigners, deported. They grant the authorities the ability, lasting initially for one year but which can be extended to two, to implement a form of house arrest and relocate a subject up to 320km from their usual residence.

But TPims were far less restrictive than the Control Orders they replaced. Introduced in 2005, the orders allowed the authorities to place individuals under 16-hour curfews, ban them from meeting other people as well as from using mobile phones and the Internet.

Following criticism that the orders were unfair and oppressive, the David Cameron coalition government — which included Mrs May as Home Secretary — watered them down.

The effectiveness of TPims has in turn been criticised as too loose by experts, who also question how security agencies will monitor suspects when the TPims expire after two years.

Experts also say the United Kingdom’s Human Rights Act, introduced by a former Labour government in 1998, has played a crucial role in restricting the scope of counter-terrorism measures in Britain. In 2004, the House of Lords declared that a set of emergency UK anti-terror laws drawn up in the wake of the Sept 11 attacks in the United States — which allowed terror suspects to be detained without charge —were incompatible with human rights. The laws were replaced the next year.

The Human Rights Act has also had a major influence on which foreign terror suspects can be deported from Britain for preaching hate, or actually planning an atrocity. This means figures such as Egyptian cleric Abu Hamza, who preached Islamic fundamentalism and militant Islamism, span out their appeals for years rather than face swift removal. At least 20 foreign terrorists have used the Act to stay in the UK, The Telegraph reported in 2015.

“We have been very careful with regard to lawfulness and ensuring that, wherever possible, Muslims do not feel discriminated against,” said Buckingham University professor of security and intelligence Anthony Glees. “We have tried to make extremism something that is just not worth the risk, but despite all this we are clearly still generating jihadists.”

Prof Glees added: “I have come to the view that we have been too susceptible to the civil liberties lobby — people who say we are a multi-cultural society and two sets of core values can sit happily side-by-side in the UK.”

Dr Sally Leivesley, managing director of Newrisk, a London-based risk consultancy, said a critical issue for the UK government is to legislate in such a way that behaviour and intention to act against the state fall within the law and can lead to prosecution. “The interpretation of Human Rights Convention causes much ambiguity on whether the terrorist as an individual needs protection even when this creates a risk to public security,” she said.

“A new approach may be needed through the expert knowledge of international lawyers to develop a solution by defining the word ‘risk’ in the convention so that governments are given a duty to protect the population against the interests of the individual, and the balance of evidence for this is not the same weighting that is used currently in the courts.”

Mrs May talked tough as she addressed the nation on Sunday, the morning after the attack at London Bridge and Borough Market. “There is, to be frank, far too much tolerance of extremism in our country,” she said.

Her comments were criticised as political and brought concerns about whether, if re-elected, her anti-terrorism plans could be effective and also protect civil liberties. In her remarks, she announced a review of counterterrorism policy, harsher sentences for terrorism offences, and an effort to crack down on “safe spaces” online and in self-segregated Muslim communities that can harbour extremism.

British police and security services already have some of the most powerful surveillance laws in the world. Surveillance cameras are everywhere, especially in cities, and there are relatively few restrictions on the mass collection of telephone and Internet data by the government.

“But the government uses those powers very carefully, which shows how the unspoken consensus here works,” said Dr Peter R Neumann, a professor of security studies at King’s College London, noting that the country has no written Constitution.

In countries with written Constitutions, such as Germany and the US, “you can define extremism as those opposed to the precepts of the Constitution”, Dr Neumann said. He pointed to the case of Anjem Choudary, a lawyer who managed to avoid breaking the law while spending nearly two decades preaching jihadi views. He was convicted last year, only when film emerged of him pledging allegiance to the Islamic State, and he was sentenced to five years and six months in prison.

One of the London assailants was influenced by Choudary.

“Choudary was for years the single person most responsible for Islamist recruiting and propaganda, but he wasn’t charged until 2015, when May had been Home Secretary for five years,” said Dr Neumann. AGENCIES