The country's biggest fire brigade has unveiled plans to save £2 million over the next five years by cutting "unnecessary" overtime.
A report to London's Fire and Emergency Planning Authority said the capital's brigade could cut "pre-arranged" overtime by £400,000 a year through closer analysis of how it arranges cover for staff at fire stations.
The Fire Brigades Union (FBU) said the move was aimed at "masking" the fact that the brigade was 150 firefighters understrength.
The authority's chairman, Brian Coleman, ordered a report following last year's strikes by FBU members in London which led to the brigade removing 27 appliances as part of its contingency plans.
Mr Coleman said: "Taxpayers expect a world-class service from the London Fire Brigade but they also expect their money to be spent wisely. As a result of last year's industrial action, we've learned that by scrutinising more closely what staff we need, where and when, we can keep London just as safe but at less cost.
"Last year, the brigade had to cope with strike action that included two eight-hour walkouts and months where firefighters worked to rule. This forced us to do things differently. If, as a result of industrial action, we have identified ways to make savings in how we work without affecting the service we provide, we have a duty to change."
Ian Lehair, a London official of the FBU, said the report was "play acting" by Mr Coleman, adding: "It's not firefighters or their union who want overtime - it's the London Fire Brigade, to mask the fact that they are about 150 firefighters understrength. The brigade is using overtime to mask shortages."
The FBU has raised doubts about the finances of AssetCo, which owns and maintains all of London's fire engines and provided emergency cover during last year's dispute over shift patterns.