The Conservatives are “signalling Islamophobia is acceptable” in the party by ignoring anti-Muslim sentiment among their ranks, a leading anti-racism charity has warned.

Hope Not Hate’s 2019 State of Hate report will accuse the Tories of being “in denial” and failing to take seriously complaints about both activists and high-profile politicians. 

Party chairman Brandon Lewis said in June Islamophobia was “utterly unacceptable” as he ordered Tory associations to compile reports about complaints in their area. 

Party chiefs have so far refused to launch an inquiry, despite demands from the Muslim Council of Britain, Tory peer Baroness Warsi and Mohamed Amin of the Conservative Muslim Forum. 

In August, Lewis launched an internal inquiry into the former foreign secretary Boris Johnson following comments he made in a national newspaper comparing women in burqas to “letterboxes” and “bank robbers”. 

A panel found Johnson’s comparison, which he made in a Daily Telegraph article to argue against a face-veil ban, was “respectful and tolerant” and that the MP was entitled to use “satire”.

Calls made in May for a broader, independent probe were rejected by vice-chairwoman Kemi Badenoch as having a “political motive”, despite Warsi, a former chair of the party, saying prejudice was “very widespread”. 

A spokeswoman for the Conservatives said the party takes swift action when reports are made.

She said: “When cases have been reported centrally, the Conservative Party has consistently acted decisively, suspending or expelling those involved and launching an immediate investigation.”

There have been several instances of Islamophobia in recent months, the report underlines, including:

• MP Bob Blackman sharing a story with the headline “Muslim Somali sex gang say raping white British children ‘part of their culture’.” Blackman also hosted the anti-Muslim activist Tapan Ghosh – who calls all Muslims “jihadis” and has defended the genocide of the Rohingya community in Burma – in parliament.

• MP Michael Fabricant posting a cartoon showing Sadiq Khan’s head on an inflatable balloon, engaged in a sex act with a pig. Khan is a Muslim, and eating pork is a sin in Islam.

• A number of MPs and councillors found to be members of a pro-Tory Facebook group littered with anti-Muslim comments such as “we should ban Islam”, it is “a threat to our country” and a “mental illness”. The MPs, who included Jacob Rees-Mogg and Andrew Rosindell, claimed they had no knowledge of it.

• Shaun Bailey, the Tories’ candidate for London Mayor, was found to have retweeted a picture accusing Sadiq Khan of being “anti-British” and calling him “mad mullah Khan of Londonistan”. 

• Numerous suspensions of Tory councillors over Islamophobia, some of whom have been reinstated with little action taken 

There was also criticism of the 2016 London mayoral campaign as “dog whistle politics” after Zac Goldsmith’s campaign made baseless claims that Muslim mayor Sadiq Khan supported “extremists”. 

Concerns have also been raised about a number of anti-Muslim posters coalescing around groups claiming to support high-profile Conservatives, including one on Facebook called the “Jacob Rees-Mogg Supporters’ Group”. 

There is no suggestion that Rees-Mogg himself is connected to the group.  

A Hope Not Hate activist told HuffPost UK: “We’ve called out Brandon Lewis a number of times over Boris and others for their comments, and he’s responded on Twitter several times back, stating there’s no problem. There appears to be startling inaction, despite others like the MCB, Tell MAMA and Baroness Warsi calling for more to be done.”

Poll data used for the report, shared with HuffPost UK, shows attitudes towards Muslims among Conservative voters have hardened over the course of eight years. 

A YouGov poll of around 10,000 people by the organisation found that 47% believed Islam is incompatible to the British way of life, and 47% think there are no go areas in Britain where sharia law dominates and non-Muslims cannot enter.

HNH’s research also found that just 11% of Muslim voters chose the Conservative party in the 2017 general election and just 19% of black and minority ethnic (BAME) voters endorsed the Conservatives in the last election – down from 23% from 2015.

Nick Lowles, chief executive of Hope Not Hate, said a failure to tackle Islamophobia could repel voters at the next election. 

He said: “There remains a stark political issue here for the Conservatives.

Iman Atta, director of the anti-Islamophobia charity Tell MAMA, said the charity had held two meetings with Lewis over anti-Muslim rhetoric in party branches and from elected politicians.

“They have taken the decision to act internally on such complaints when we have offered assistance,” she said. “That is their prerogative though it is clear that some local associations need training and support in reducing some of the divisive anti-Muslim rhetoric that activists and even some elected members have said and circulated online.”

Atta added the Tories acted quick when complaints were raised but said the party had a “core problem” and Tory associations needed a “road map” to deal consistently with the issue. 

She said: “We also cannot get away from the fact that politicians like Boris Johnson have literally carved a fault line between some Muslim communities and the Conservatives around his comments on Niqab-wearing Muslim women.”

A Conservative spokesman added: “The swift action we take on not just anti-Muslim discrimination, but discrimination of any kind is testament to the seriousness with which we take such issues.”

It comes as the Labour Party was once again faced with claims of anti-Semitism among its grassroots, with Jewish MP Luciana Berger thought to be on the brink of resigning.

General secretary Jennie Formby also last week faced claims from MPs she was covering up the number of complaints about Jew-hatred allegedly displayed by members and activists – something the party denies.