Firefighters held a protest outside City Hall on Wednesday morning as Boris Johnson faced the London Assembly for this month's Mayor's Question Time.
10 fire stations – including Southwark Fire Station – face closure under plans imposed by the Mayor of London despite the opposition of the London Fire & Emergency Planning Authority (LFEPA).
"There is widespread hostility to these cuts which would lead to an increase in response times for four million Londoners," said Paul Embery of the Fire Brigades' Union.
"In a service where seconds really do count, this would inevitably cost lives. The mayor should abandon his plans and keep his pre-election promise not to cut fire cover in London."
During the session Labour assembly member Andrew Dismore reminded Mr Johnson that he had previously pledged that there would be no reduction in the number of fire stations and appliances
Mr Johnson, who argues that despite the cuts response times will be maintained and safety improved, replied by telling Mr Dismore to "get stuffed".
After a reprimand from London Assembly chair Darren Johnson the Mayor apologised for the remark.
LFEPA – which has a Conservative chair but not a Tory majority – will meet on Thursday at the fire brigade's Union Street headquarters to consider the latest legal advice on the Mayor's decision to use his power of direction to overrule the authority.
Southwark is one of a number of London councils which has threatened the Mayor with legal action if he presses ahead with the proposed cuts.