Baroness Warsi, the first Muslim woman to serve in cabinet, revealed she has spent two-and-a-half years raising the issue within the party.
The Muslim Council of Britain (MCB) has now called on the Tories to launch an independent inquiry into allegations of Islamophobia.
The group said the last month it had seen weekly incidents of Islamophobia from Conservative representatives and candidates.
Baroness Warsi told Sky News the issue was a long-running one for the Tories and “was an issue for us long before the issue of anti-Semitism within the Labour Party became public”.
She said: “I’ve raised this issue with successive chairman, I’ve raised the matter informally, I’ve raised it formally, I’ve had meetings about it, I’ve even written to the prime minister.
“I wrote to her last year about this issue, and each time it seems that we’ve kind of said ‘yes, we take these issues very seriously’ and then shrugged our shoulders and moved on.
“What’s really concerning for me is that the frequency of these incidents seems to be now increasing, whether that’s because there’s now more public awareness about reporting these issues.
“I hope, sincerely, the party now will deal with it.”
Baroness Warsi, who served as Conservative chair between 2010 and 2012, said she held a zero-tolerance approach to “any form of bigotry” when at the head of the party.
She added: “That zero tolerance approach needed to continue. Unfortunately it hasn’t.”
The Tory peer pointed to the “terrible Islamophobic, anti-Muslim campaign” run by Conservative candidate Zac Goldsmith in the London mayoral election in 2016, an allegation Mr Goldsmith at the time described as “absurd”.
The MCB said alleged incidents have included Conservatives tweeting that “the Prophet Mohammed was a f****** paedophile”, calling Islam the “new Nazism” and sharing articles that called Muslims “parasites”.
In a letter to party chair Brandon Lewis, MCB criticised the party for failing to take action against MP Bob Blackman.
Last October, Mr Blackman hosted a parliamentary event attended by Tapan Ghosh, a Hindu nationalist who describes himself as “determined to fight against Islamic aggression and expansion”.
Speaking to Sky News at the time, Mr Blackman said he was unaware of Mr Ghosh’s past comments prior to the event and would not have been able to prevent his appearance had he wished to.
In March, the MP also expressed “regret” after being criticised for sharing a Facebook post from an anti-Muslim US website.
Mr Blackman previously shared a Twitter post by Tommy Robinson “in error” and said he condemned the views of the English Defence League co-founder.
This week he was revealed to have been a member of a number of far-right Facebook groups.
Mr Blackman said: “I utterly refute this allegation. I was added to Facebook groups without my knowledge or permission and immediately removed myself from them when I became aware I had been added.
“I did not host Tapan Ghosh in parliament. He was invited by an organisation without my knowledge.
“In the past I shared a social media post in error which I apologised for at the time. I will continue working will all communities in my constituency and I condemn Islamophobia.”
In a statement responding to the MCB letter, a Conservative spokesperson said: “We take all such incidents seriously, which is why we have suspended all those who have behaved inappropriately and launched immediate investigations.”
Many of those named in the MCB letter have been noted as being suspended by the party, but Mr Blackman remains an MP.
Since being made party chairman in January, Mr Lewis has launched a code of conduct for MPs and local election candidates and encouraged members to email him if they hear of bigotry.