Baroness Warsi has criticised her party's inquiry into Islamophobia and other forms of prejudice, arguing it does not address past problems.
The former Conservative chairwoman said it needed to cover previous cases rather than just complaint handling.
And she said the party's choice of a psychiatry professor, who she claimed did not believe in institutional racism, to head it did not "bode well".
Prof Swaran Singh was announced as the chairman of the inquiry on Tuesday.
Speaking on BBC Politics Live, Tory MP Suella Braverman defended the inquiry as a "welcome step".
"What I think this does show is the robust and swift action that Boris Johnson is taking on this issue," she said.
But speaking earlier to Radio 4's Today programme, Baroness Warsi said in order to be "credible" the inquiry needed to cover "everything that has happened over last four years".
"Unfortunately the remit of the inquiry does not cover that," she said.
"All it does is to see how we can improve our process.
"There is no look at what has actually gone on, no look at the extent of the cases, no detail of how bad the problem has been and how badly it has been dealt with."
She also criticised the appointment of Prof Singh - the former commissioner of the Equality and Human Rights Commission, the watchdog currently investigating anti-Semitism allegations within Labour.
"The Runnymede Trust [a race equality think tank] encapsulated it when they said he is somebody who believes racism is a contested term and that institutional racism simply doesn't exist.
"That gives an indication of where the inquiry will end up," she said.
The Muslim Council of Britain said the appointment of Professor Singh was "at risk of being seen in the same light as the Conservative Party's customary approach to Islamophobia, that of denial, dismissal and deceit".
It also criticised the scope of the inquiry saying: "We were promised an independent inquiry into Islamophobia specifically - now we have a review that aims to broaden the scope to examine discrimination more generally.
"A laudable aim if it were not for the fact that the Conservative Party is afflicted with a particular type of bigotry which it refuses to countenance."
The Conservatives said Prof Singh would look at how it could improve its procedures and ensure "any instances are isolated and that there are robust processes in place to stamp them out".
Conservative Party chairman James Cleverly said his party was committed to stamping out "unacceptable abuse".
"The Conservative Party has always worked to act swiftly when allegations have been put to us and there are a wide range of sanctions to challenge and change behaviour," he said.
"The Conservative Party will never stand by when it comes to prejudice and discrimination of any kind and it is right to hold an independent review, so we can stamp out unacceptable abuse that is not fit for public life."
During the general election campaign Conservative leader Boris Johnson apologised for "all the hurt and offence" that has been caused by Islamophobia in his party.
The prime minister has previously been criticised for saying Muslim women wearing burkas "look like letter boxes".