It is understood that officials will identify the most dangerous extremists from countries including Afghanistan, Pakistan, and Indonesia and add them to a warning list.
Anyone on that list will be refused entry.
The development follows Rishi Sunak’s speech in Downing Street on Friday, in which he said streets had been “hijacked by small groups who are hostile to our values and have no respect for our democratic traditions”.
Ministers already have powers to block people who are “non-conducive to the public good”.
Those powers are generally used to prevent people who are known to threaten national security from coming to the UK.
Ministers believe they can make greater use of them to include individuals preaching racism, incitement, or using intimidation or violence to undermine the democratic process.
PM urges police action on Gaza protests
Home Office officials are considering tackling what are described as far-left anti-democratic organisations amid concerns they are making common cause with Islamist groups.
Lord Walney, the government’s independent adviser on political violence, has been working on a review.
In that document, he is “asking the leader of every mainstream political party to take a zero tolerance approach to the menace that is threatening our democracy”, he wrote in The Sun.
There has been an “unholy alliance between far-Left groups and some of the Islamist extremism that has been seen on the [pro-Palestinian] marches”, Lord Walney told The Telegraph.
Earlier, Sadiq Khan, the mayor of London, said there is a “concerted attempt” to “humiliate minorities for political gain”.
A Home Office spokesperson said: “Extremism has no place in our society and we will not tolerate tactics that set out to intimidate, threaten or cause disruption to the law-abiding majority.
“In recent months, we have also witnessed a small number of protesters display violent and hateful behaviour, and the police have our full support in tackling extremism and hate crime.
“We are considering the report’s recommendations extremely carefully and will respond in due course.”
