Keir Starmer has called on people to “open their eyes to Jewish pain” in the wake of the Golders Green terror attack, and accused anyone marching alongside supporters of Hamas of “venerating the murder of Jews”.

The prime minister made his strongest ever remarks on antisemitism after visiting the area of the attacks for a meeting with emergency workers and community leaders.

His presence was greeted by heckling from Stop the Hate protestors, a group campaigning against antisemitism, with one branding him a “traitor” for failing to keep Jews safe.

In a statement in Downing Street, Starmer said new powers were needed to protect the Jewish community after the stabbing attack, which was “not a one-off”. Two Jewish men were hospitalised with knife wounds.

“Antisemitism is an old, old hatred, history shows that the roots are deep, and if you turn away, it grows back,” he said. “Yet, far too many people in this country diminish it. They either don’t see it or they don’t want to see it.”

He strongly criticised people who march alongside supporters of Hamas without calling it out. However, the government has stopped short of endorsing the idea of a pause on pro-Palestine marches, which has been suggested by Jonathan Hall, the independent reviewer on terrorism.

In his statement, Starmer said: “Of course, we protect freedom of speech and peaceful protest in this country, but if you are marching with people wearing pictures of paragliders without calling it out, you are venerating the murder of Jews.

“If you stand alongside people who say ‘globalise the Intifada’, you are calling for terrorism against Jews, and people who use that phrase should be prosecuted.

“It is racism, extreme racism, and it has left a minority community in this country scared, intimidated, wondering if they belong.”

Starmer also pledged more funding for Jewish security services and stronger powers to shut down charities that promote antisemitic extremism.

“We will prevent hate preachers from entering our country, bar them from our campuses, our streets, our communities. Work with our justice system to speed up sentencing on antisemitic attacks so there is a stronger deterrence factor,” he said.

“And we need stronger powers to tackle the malign threat posed by states like Iran, because we know for a fact that they want to harm British Jews, which is why we will fast track the necessary legislation”.

Shabana Mahmood earlier promised to “do everything in my power” to keep British Jews safe, as police said the suspect in the stabbing of two men on Wednesday was a 45-year-old British national born in Somalia.

The government said a further £25m would be invested to increase security for Jewish communities after the suspected terrorist attack. The funding will be aimed at boosting police patrols and protection around synagogues, schools and community centres. But the government is facing pressure to go further, including calls to ban pro-Palestinian marches.

Legislation creating proscription-like powers to pursue people and organisations acting on behalf of malign state-sponsored groups will also be “fast-tracked” in the coming weeks,

It is understood the draft laws will be included in the king’s speech setting out the government’s legislative agenda for the next parliamentary session on 13 May.

The home secretary said the suspect, named as Essa Suleiman, was born in Somalia and came to the UK lawfully as a child in the 1990s and was a British national. She said the two victims, Shilome Rand, 34, and Moshe Shine, 76, continued to be treated in hospital and were in a stable condition.

The Metropolitan police commissioner, Mark Rowley, said on Wednesday the individual in custody had a “history of serious violence and mental health issues”.

Speaking on BBC Breakfast, Mahmood said she understood “the very real fear that is being felt” in the Jewish community. “The government has already been responding, and we are now doing more as well,” she said. “We will always take every step within our power in order to keep our community safe.”

Police are treating the stabbing of two men in Golders Green, which happened just after 11am on Wednesday, as terrorism, with the suspect described as having been allegedly looking for anyone “visibly Jewish” to attack. The stabbings follow a series of arson attacks on Jewish targets in London since March, including two previous incidents in Golders Green.