The Mayor made the comment whilst being questioned by Labour Assembly leader Andrew Dismore over planned reductions to fire fighting services.
“How can cutting fire stations, cutting fire engines and cutting firefighters post not be a reduction in fire cover?” Mr Dismore asked.
“You’ve lied to the people of London,” he added.
To which Mayor Boris Johnson replied: “get stuffed.”
The Mayor was asked to withdraw the remark and apologised saying “it just popped out”.