The head of the Metropolitan Police has called on the government to "change or clarify" the law following the arrest of comedian Graham Linehan over posts he made online.
The 50-year-old was arrested under the Public Order Act on Monday on suspicion of inciting violence in relation to posts about trans people on X.
On Wednesday, Met Commissioner Sir Mark Rowley defended the officers involved, but said he recognised "concern caused by such incidents given differing perspectives on the balance between free speech and the risks of inciting violence in the real world".
Sir Keir Starmer said the police must "focus on the most serious issues" when asked in the Commons about the arrest.
His arrest has prompted a backlash from some public figures and politicians, who have said it raises questions about free speech in the UK.
Earlier on Wednesday, Health Secretary Wes Streeting said the government needed to "look at" the relevant legislation following the arrest, adding ministers "want the police to focus on policing streets rather than tweets".
Linehan has said his arrest at Heathrow was related to three posts on X from April.
The first post called it a "violent, abusive act" for a trans-identified male to be in a female-only space. He wrote: "Make a scene, call the cops and if all else fails punch him in the balls."
Linehan has been bailed under investigation and has not been charged with an offence.
In his statement on Wednesday, Sir Mark said the decision to arrest Linehan "was made within existing legislation - which dictates that a threat to punch someone from a protected group could be an offence".
Sir Mark said his officers "had reasonable grounds to believe an offence had been committed," but that police more broadly had "been left between a rock and a hard place" when investigating online speech.
He continued: "I don't believe we should be policing toxic culture wars debates and officers are currently in an impossible position."
Sir Mark said police will have to "make similar decisions in future unless the law and guidance is changed or clarified".
He said he hopes this happens "without delay", but said the Met would be taking immediate action to update how it decides which cases warrant a police investigation.
Sir Mark said: "As an immediate way of protecting our officers from the situation we find ourselves in today, we will be putting in place a more stringent triaging process to make sure only the most serious cases are taken forward in future – where there is a clear risk of harm or disorder."
Linehan, who came to prominence after writing sitcoms Father Ted and the IT Crowd, and has since become a vocal activist who is highly critical of the trans-rights movement.
In an online article recounting his arrest, Linehan, 57, said he was detained by five armed officers who were waiting for him at Heathrow Airport, where he was returning to from the US.
He said he was taken into custody for questioning and later escorted to hospital after a health check revealed he was suffering from high blood pressure levels.
The Irish comedian also faces a charge of harassment related to a separate incident. He denies that alleged offence and is due to appear in court on Thursday.
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