The mayor of London, Sadiq Khan, has challenged the Conservatives to adopt a new definition of Islamophobia, saying that he has been repeatedly subjected to anti-Muslim abuse from Tory members and supporters.

In a letter to Theresa May, Khan calls on the prime minister to order her party to deal with the issue. He says it must be among measures taken to reassure British Muslims about their safety in the aftermath of the Christchurch terrorist attack. He warns that the massacre demonstrates “the consequences of failing to root out Islamophobia and anti-Muslim sentiment from our society”.

Dozens of Tory members were suspended over alleged anti-Muslim comments last week. The number of hate crimes against Muslims reported across Britain increased by 593% in the week after the attack on two New Zealand mosques.

Khan called for May to back the adoption of a definition of Islamophobia drawn up by the all-party parliamentary group for British Muslims, already accepted by Labour and the Lib Dems. The definition reads: “Islamophobia is rooted in racism and is a type of racism that targets expressions of Muslimness or perceived Muslimness.”

Khan writes: “Reassuring British Muslims about their safety in the aftermath of Christchurch is not just about policing and security. It also requires us to relentlessly root out the Islamophobia and anti-Muslim abuse that has crept into the mainstream of our society and political debate. It is vital that our political parties lead from the front in this effort and set the strongest possible example to society.

“The Conservative party in particular needs to do much more to send the clear message that Islamophobia is totally unacceptable, as unfortunately that has not always been the case over recent years.

“I myself have repeatedly been subject to Islamophobic abuse from Conservative members and supporters. I have lost track of the number of Conservative councillors and members that have been suspended or faced legal action as a result of making Islamophobic comments towards or about me.”

He also attacks the Tories’ London mayoral candidate Shaun Bailey for retweeting an article that referred to Khan as “the mad mullah of Londonistan”. Bailey’s team have said he had not seen the offensive remarks when he retweeted the material. Bailey has since said that his party must “root out” Islamophobia and have a “proper conversation” about the issue.

Zac Goldsmith, who was Khan’s Tory opponent when he first stood for mayor in 2016, was also accused of running a campaign that pandered to Islamophobia.

“But this is not about me,” Khan writes. “I am deeply concerned about the message these incidents send to our wider society. This is not about party politics – it is far more important than that.

“You will know that I have rigorously called out racism wherever I have seen it – including on antisemitism within the Labour party.

“Adopting the all-party parliamentary group definition of Islamophobia will send the strongest possible signal that there is no place for Islamophobia or anti-Muslim sentiment in the Conservative party or anywhere else in our politics or wider society.”

A Conservative party spokesperson said: “We are deeply concerned at hatred directed against Muslims and others because of their faith or heritage. Any form of discrimination or abuse is wrong and the strong action we take on anti-Muslim discrimination is testament to the seriousness with which we take such issues. We know some have suggested that establishing a definition of Islamophobia could strengthen efforts to confront bigotry and division. Any such approach would need to be considered carefully.”