Ms Alinejad spoke at the Sir Harry Evans Global Summit on investigative journalism in central London on Wednesday and described what happened when the police officers arrived.
"After my appearance on Piers Morgan's show last night, the team from Metropolitan Police came to my hotel and they said that everywhere you go, we have to protect you," she said.
"They're all actually using the resource of the UK people to protect me, but I am here to ask the UK government to protect democracy because right now journalists are under threat.
"When I see Metropolitan Police around me, I'm not relaxed because it shows you the level of threat."
Ms Alinejad appeared on Morgan's show to discuss her campaign against Iran's clerical regime and for women's rights in the country.
“I'm very loud against terrorists — I’m not scared of them,” she told Morgan.
Recalling being the target of an Iran-backed assassination plot in the US, she said: “It's scary when you see a man with a loaded gun in front of your house trying to kill you.
“The Islamic Republic hired three [members of the] Russian mafia and they were trying to kill on US soil.
“The FBI arrested them and right now they are in prison.”
Ms Alinejad said it was still “scary” but said it showed that Iran is “scared of me and millions of women like me”.
After Morgan called her a hero for her campaign, she said: “My heroes are in Iran. They know that they're facing guns and bullets.
“Some of them get shot in their eyes and they are blinded.
“But they say that you can take our life, you can take our eyes, you can take our bodies, but not our hope. We are here to end this regime.”
Ms Alinejad is in the UK to meet members of Parliament and promote her campaign against the Iranian government.
“It's not about us trying to just save ourselves,” she said. “The Islamic Republic is a threat to democracy.
“And we are actually risking our life to protect democracy across the globe.
“The Islamic Republic is sending drones to [Russian President Vladimir] Putin to kill innocent Ukrainians.”
Ms Alinejad spoke of how Tehran had hired hitmen in the UK to kill a journalist at an Iranian TV station.
“If you don't support our fight against the Islamic Republic, you have to face the terrorists on western soil,” she said.
“So clearly, what happens in Vegas [it is said] that it is going to stay in Vegas, but what happened in the Middle East in Iran is not going to stay there.
“It's going to infect the rest of the world.”
After the interview, Ms Alinejad posted on Twitter: “Last night after my appearance on @PiersUncensored @metpoliceuk sent a close protection team to my hotel because of high threat level.
“The terrorist regime of Iran is challenging the UK on its own soil.
“Now thanks to police I am speaking at #sirharrysummit to demand the UK government to protect democracy by designating the IRGC [Islamic Revolutionary Guard Corps] as a terrorist organisation.”
In another tweet, she made clear her call for action against Iran, saying: “I told Piers Morgan: The UK government must not allow Islamic Republic to have a base in the country.
“Iranian officials, unlike the British weather, are predictable in how they engage in terrorism in the West.
“Isolate gender apartheid.”
Speaking at the summit on Wednesday, Ms Alinejad said she had met French President Emmanuel Macron and Dutch Prime Minister Mark Rutte.
She said that despite many meetings with leaders of democratic countries, all they had was "empty words and empty condemnations".
"They never stopped the Iranian regime from killing innocent people," Ms Alinejad said.
"I was really not angry when I saw that President Macron shake the hand of [Iranian President] Ebrahim Raisi, right after the massacre happened in Iran."
Ms Alinejad said she complained after the event, saying "France is all about diplomacy. But I said no.
"France is also about revolution and the West is also about democracy. It's about equality. It's about feminism."
"Still we see democratic countries trying to get back to the negotiation table.
"No, we need concrete actions."
Ms Alinejad said women in Iran were still protesting, but they were closely watching women in the West.
"The time has come that we have to stick with women of Iran and Afghanistan," she said.
"If not, believe me, we are going to face Taliban and Islamic Republic on UK soil.
"The UK government has an important role. They have to take the lead."
Speaking about the failed assassination and kidnap attempts in the US, Ms Alinejad said: "We are not scared of our lives at all because people inside Iran are sacrificing their lives.
"They are facing guns and bullets and executions.
"But what is scary is that the UK government, the US government, the western countries, they are allowing the terrorist regime to challenge them on western soil.
"This is scary."
Ms Alinejad, who left Iran in 2009 and has been living in the US since 2014, became an international phenomenon when she launched a Facebook page inviting Iranian women to post pictures of themselves without a hijab.
With a social media following of more than eight million, she considers herself “a channel for the voiceless”.
The FBI uncovered a plot on Ms Alinejad's life last year. It followed a separate foiled kidnapping attempt tied to Iran in 2021.
Iran has denied any involvement in the plots against Ms Alinejad.