The Metropolitan Police Federation has backed Commissioner Dame Cressida Dick following calls for her to be replaced.
A number of high-profile signatories wrote an open letter accusing her of "presiding over a culture of incompetence and cover-up".
This came after reports Dame Cressida, 60, had been offered a two-year extension to her contract.
In a statement, the federation said it "fully supports" the contract extension.
Since her appointment in 2017, Dame Cressida has been involved in several controversies.
The federation, which represents more than 30,000 officers in London, is the staff association to which every constable, sergeant, inspector and chief inspector in the Metropolitan Police Service belongs.
In its statement backing Dame Cressida, it said: "It is easy to comment and criticise from the side-lines."
Ken Marsh chairman of the Metropolitan Police Federation said Dame Cressida had the "full support of the rank and file".
He said he understood "fully" the position of the letter signatories and that his "heart goes out to them".
Asked about criticism of Dame Cressida, he said: "From what I've seen she's done everything she can to answer all comments that are put to her and everything that's put in front of her."
A full statement from the Police Federation said: "Whilst the federation does not always agree with the commissioner - the same goes for anyone who holds that post - we think she is doing a good job in difficult circumstances.
"Many of the voices we hear calling for the commissioner to go are the same ones who, following the Clapham Common vigil earlier this year, rounded on our colleagues criticising their work.
"They were, of course, proven to be completely wrong when Her Majesty's Inspector of Constabulary looked at the policing of the event.
"We have worked with this commissioner for a number of years now and believe she is still the best candidate for the role.
"We know her to be an ethical, courageous and highly competent police leader who genuinely cares about London, its citizens and her officers."