On 15 March, a gunman walked into the Al Noor mosque in Christchurch, New Zealand and opened fire. During the course of his killing spree there, and at the Linwood Islamic Centre, 51 people were slaughtered in their place of worship for no other reason than their killer had decided that their faith meant that they deserved to die.

Hatred against Muslims does not begin with the sound of gunfire breaking through the peaceful calm of a place of prayer. It begins with simple prejudice in our schools, our workplaces and our communities. More than 20 years since the Runnymede Trust published its seminal report, Islamophobia: a challenge for us all, it is on the rise.

The all-party parliamentary group on British Muslims, which I lead with Anna Soubry, is determined to meet this challenge. That’s why we have produced a report establishing, for the first time, a working definition of Islamophobia. It was clear from the evidence we gathered, including powerful testimony from the victims of Islamophobia, that what we’re up against goes wider than anti-Muslim hatred. It is structural, often unconscious, bias.

So we argue that “Islamophobia is rooted in racism and is a type of racism that targets expressions of Muslimness or perceived Muslimness”. We’ve produce a series of examples, modelled on the IHRA definition of antisemitism, to help people understand how this manifests: the attempted murder of a Muslim woman and her 12-year-old daughter as “revenge” for the Parsons Green terror attack; the torture of a Muslim convert by two women in Guisborough, while they shouted “We don’t like Muslims over here”; the Muslim mother attacked for wearing a hijab on the way to collect her children from primary school in London; the “punish a Muslim day” letters sent to Muslim institutions, and prominent Muslim figures; the racists in Northern Ireland who left a pig’s head on the door of the mosque they had graffitied; the motorists forking out £1,000 more to insure their car if their name is Muhammad; the Social Mobility Commission’s findings of conscious and unconscious bias against Muslims in the employment market; the Islamophobic abuse hurled at people who aren’t even Muslim, because their abusers couldn’t tell the difference between, for example, a Sikh wearing a turban and a Muslim man; the men who tied bacon to the door handles of a mosque in Bristol.

We toured the length and breadth of the country, engaging in extensive consultation with Muslim communities, academics, lawyers, police officers, public services, civil society leaders and politicians. As a result of this, our definition already has widespread backing, including from more than 750 British Muslim organisations – including the Muslim Council of Britain, Muslim Women’s Network and British Muslims for Secular Democracy – as well as the first minister of Scotland, the mayor of London and local authorities across the country.

So it is particularly disappointing to see a noisy chorus of vocal opposition making arguments in bad faith that accuse us of trying to use the term Islamophobia to shut down criticism of Islam and introduce blasphemy laws by the back door. In fact, our report makes it crystal clear that our definition does not preclude criticism of Islam or Islamic theology. God, if you believe in such a thing, doesn’t need protection from criticism.

I have watched, with some amazement and even greater despair, the Conservative party making exactly the same mistakes over Islamophobia within their own party as the Labour party has with antisemitism: the dismissal, denial and delegitimisation of serious concerns raised by prominent Muslims about racism within their ranks. Theresa May could have followed the lead of the Scottish Conservative leader, Ruth Davidson, in backing this definition, and by so doing left a powerful legacy to detoxify her party and improve the lives of Muslims across the country. Instead, with a remarkable lack of self-awareness and humility, the party that has so spectacularly failed British Muslims now intends to produce a government definition. Its abject failure to understand and tackle Islamophobia within its own ranks suggests it has neither the wisdom nor the credibility to do so.

Given that, just over a year ago, government ministers denied that there was a need for any definition at all, I suppose we might consider this latest development some sign of progress. But it is too slow and will not be tolerated. British Muslims deserve better and this is, as the Runnymede Trust said again last year, a challenge for us all.

• Wes Streeting is the co-chair of the all-party parliamentary group on British Muslims