Adopting an official definition of Islamophobia could hinder British counter-terror efforts, a police chief has claimed.
Martin Hewitt said the proposed wording could 'undermine many elements of counter-terrorism powers and policies'.
In a letter to Theresa May he said it could prevent authorities from shutting down extremist groups or conducting searches at ports.
Advocates of an official definition believe it could help Muslims report crime against them and improve relations between Islamic communities and the government.
But critics say it could restrict legitimate debate about Islam and confuses criticism of the religion with hatred of individual Muslims.
MPs will discuss the matter tomorrow.
Adopting an official definition of Islamophobia could hinder British counter-terror efforts, a police chief has claimed (file photo: armed police officers in London)
There is no specific law against Islamophobia in the UK.
However, there are numerous laws which might be used to prosecute offenders.
Stirring up religious hatred is an offence under the Public Order Act 1986.
It can carry a sentence of up to seven years in prison.
Criminals may also be handed longer sentences for other offences if they are found to have been motivated by racial or religious hostility.
There are separate laws covering online abuse.
In addition, the Equality Act 2010 stops discrimination based on 'protected characteristics' including religion.
If a new, official definition is adopted, it could be used to block government actions in the courts.
Terror legislation could be subject to such judicial reviews, it is claimed.
An unofficial 1997 wording defined Islamophobia as 'unfounded hostility towards Muslims'.
The suggested new one says: 'Islamophobia is rooted in racism and is a type of racism that targets expressions of Muslimness or perceived Muslimness.'
The proposed definition calls Islamophobia a 'type of racism that targets expressions of Muslimness or perceived Muslimness'.
Mr Hewitt, chairman of the National Police Chiefs' Council, said an official wording could weaken terror laws and prevent stop-and-search at ports, The Times reported.
The term was 'perhaps misleading in the context of hate crime... hate crime seeks to protect Muslims and not Islam,' he warned the Prime Minister.
A group of opposition MPs led by Labour's Wes Streeting and Anna Soubry of Change UK have pushed for an official definition.
The group, chaired by Ms Soubry, recently published a 72-page report arguing that 'the lack of a widely adopted working definition... has led to an increase in Islamophobia in society to devastating effect'.
A new official definition could
