Tory Party chairman Richard Holden said the party had allowed anti-Jewish racism to become mainstream.
He said Labour still has a “huge problem” and accused Sir Keir Starmer of trying to sweep recent controversies under the carpet.
It comes after George Galloway won the Rochdale by-election when Labour ditched their candidate Azhar Ali in an antisemitism storm.
“It is clear the Labour Party allowed anti-Jewish hatred to become mainstream,” the senior Tory told the Sun on Sunday.
“It has always been there in society but the floodgates opened under Jeremy Corbyn’s leadership and they are still failing to root it out.”
Sir Keir was forced to drop Mr Ali over a leaked recording of a meeting of the Lancashire Labour Party shortly after Hamas’ October 7 terror attack.
The councillor suggested Israel allowed it to happen as a pretext to invade Gaza and blamed Jewish media figures for fuelling criticism against a pro-Palestinian Labour MP.
A second parliamentary candidate and former Labour MP Graham Jones was also suspended after for saying “f****** Israel” at the same meeting.
The Tories have written to Labour demanding to know whether Mr Jones will be running for Labour because his Facebook account still suggests he is the local candidate.
Mr Holden added: “There are big questions there for the Labour Party which remain unanswered because they’re trying to sweep it under the carpet, just like they did during the Corbyn years. They are just not prepared to take this issue head on.”
The top Tory said Galloway’s return to Parliament was a crisis of Labour’s making: “Labour can try and spin this as much as they like but at the end of the day responsibility falls squarely on fact that the Labour Party has not changed one bit.”
In 2020, the Equality and Human Rights Commission (EHRC) found the party broke the law in its handling of anti-Semitism under Mr Corbyn.
Prime Minister Rishi Sunak has announced a £72 million security package for Jewish schools, synagogues and community centres.
And this week Prince William also said he was “extremely concerned” about the rise in anti-Semitism on a visit to a synagogue.
Hate crimes against Jews hit a high of 4,000 last year, according to shock figures from the Jewish Community Security Trust.
Mr Holden spoke out on a visit to the office of Tory MP Mike Freer which was hit by an arson attack on Christmas Eve.
Mr Freer, who has one of the UK’s largest Jewish populations, has said he will stand down at the next election following a series of death threats.
A Labour spokesperson said: “Keir Starmer has changed the Labour Party and taken action to root out racism within the party, particularly antisemitism.
“Rishi Sunak is too weak to stand up to Lee Anderson and Liz Truss or deal with the Islamophobia, conspiracy theories or other extreme views that appear to be tolerated within the Conservative Party.”
It is understood Mr Jones is not able to run as a Labour candidate as he is suspended.