Ms Fiaz said the retention of a 24-hour moratorium on flights from 12:30pm on Saturdays was positive, but condemned the decision to override local opposition.
She added: “I remain deeply concerned that our residents will be seriously harmed by the impact of further air-flight noise.
“We will be studying the decision notice carefully and considering all options as we remain concerned about the detrimental impacts on the health and quality of life of our residents.”
The council has six weeks to seek leave to appeal to the High Court under the Town and Country Planning Act, though the court is not bound to grant permission.
Newham has a historically uncomfortable relationship with London City, which sits cheek by jowl with some of the capital’s poorest communities.
While the airport caters largely to a financial elite based in the City and at offices in Canary Wharf, the borough ranks as London’s third-most deprived, with almost 40pc of residents living in poverty, according to council estimates.
The clash between the council and the Cabinet also sets Ms Fiaz against Ms Rayner, who helped secure her second term as mayor in 2022 in the face of local opposition.
Ms Fiaz, first elected after a Momentum campaign to oust the Labour incumbent, had been accused by her former supporters of backing cuts and gentrification, but was retained as candidate by a panel of national executive committee members that included Ms Rayner.