Southwark Fire Station could close by January 2014 after the London Fire & Emergency Planning Authority voted to approve a raft of cuts to the London Fire Brigade.
At a meeting of authority members on Thursday afternoon, chairman James Cleverly used his casting vote to approve the final version of the fifth London Safety Plan after eight members voted for the proposals, eight voted against and one member abstained.
Members of the Conservative group are said to have applauded as the plan was voted through.
Mayor of London Boris Johnson had directed the authority to approve the plan, despite opposition to the cuts from a majority of authority members.
Legal advice showed that the authority – which includes Conservative, Labour, Lib Dem and Green members – had no grounds to resist the Mayor's instructions.
The authority says it needs to make budget savings of £45 million over the next two years and the measures in the plan will achieve £29 million of those savings.
The cuts, to be implemented in January 2014, include the closure of Southwark Fire Station and nine others in London, as well as reduction in the number of firefighters.
Labour's Fiona Twycross AM said: "We are all deeply disappointed that Boris' cuts have now been forced through, we wanted to continue the fight in court.
"However, the legal advice we received was categorical and clearly stated we had no legal basis to challenge the Mayor in this way.
"If we had gone down this route then we would have spent a large amount of taxpayers' money fighting a futile battle."
She added: "Boris may be celebrating but today Londoners have lost; he should hang his head in shame.
"The London Fire Brigade does a fantastic job keeping us all safe and secure when we are at our most vulnerable.
"It is a testament to Boris' cavalier approach and arrogance that he has not listened to Londoners and protected frontline services."
Liberal Democrat Stephen Knight AM said: "After repeatedly ignoring the views of the London Assembly, the London fire authority and most importantly Londoners the Mayor has finally managed to bulldoze through his foolish plans to close one in ten of London's fire stations.
"The responsibility for 10 of London's fire stations being closed by January rests entirely with the Mayor."
Several London councils – including Southwark – have been investigating the possibility of seeking a judicial review of the Mayor's decision.
"We take this responsibility very seriously because the safety of our residents is at risk, and that is why we are preparing to seek a judicial review of the cuts.
"In Southwark, we have experienced the highest level of fire deaths of any borough over the last five years and yet the Mayor wants to reduce the number of firefighters in our borough by a third.
"It is clear that the decision-making process has been deeply flawed and we will continue to fight the cuts tooth and nail until we have exhausted all possibilities."