According to the Conservatives at City Hall, London mayor Sadiq Khan hasn't removed the Olympic precept from his first budget, and is using it to fund other projects.
It was set up before the games - but Khan promised to drop it once the £625m of funding had been collected from taxpayers by 2017.
The precept comes to £8 on the average band D property in London.
Gareth Bacon, London Assembly Member for Bexley and Bromley, said: “Sadiq Khan is trying every trick in the book to pay for his wild spending promises at City Hall, including taxing Londoners for a Games which has already been paid off.
“The mayor needs to apologise to Londoners for breaking his promise to remove this tax. He also needs to properly balance his books without using Olympic money, which was never intended to be his blank cheque.
“I will be asking for the mayor to eliminate this tax as promised, and pay for the budget shortfall by removing the outdated policy of free travel for flatmates of TfL staff.”
Bacon will propose the removal of this free travel policy from the budget, a move he says would save £24.4m.
Khan said: "This is desperate nonsense from the Tories. I have always been crystal clear to Londoners that I will keep the council tax precept as low as possible without risking Londoners' safety.
"Promise made - promise delivered, with the non-policing element frozen and Londoners paying just 8p a week more towards policing.
“I want to keep taxes as low as possible – but I am simply not willing to sacrifice Londoners safety and security.”