A federal judge in Brooklyn has refused — for the third time — to let accused Nxivm sex cult leader Keith Raniere out on bail ahead of his trial.

Raniere, 58, who has been cooling his heels at the Metropolitan Detention Center since his arrest last March, made another bid for freedom after a fire knocked out heat and power at the Sunset Park lockup last month.

His lawyers also argued that his due process rights have been violated because the case has taken too long to bring to trial — which is set to begin in April.

Prosecutors have fought to keep Raniere behind bars, saying he’s a flight risk — and in his latest order, Brooklyn federal Judge Nicholas Garaufis agreed.

“Nothing has happened since the second bail order to cause the court to alter its conclusion that Raniere is a significant flight risk,” the judge wrote in an order issued late Tuesday. “Accordingly, the court finds that the evidence justifying Raniere’s pretrial detention is strong.”

Garaufis also noted that the delay of trial is because of “the inherent complexities of this large multi-defendant case, which presents defense counsel with voluminous discovery to absorb and the court with myriad motions to address.”

Raniere and several others — including one-time “Smallville” actress Allison Mack and Seagram’s liquor heiress Clare Bronfman — are all facing charges over a group within Nxivm where “slave” women were allegedly instructed to have sex with Raniere, get his initials branded into their skin and maintain near-starvation diets.

Mack — wearing her hair in a bun with a penxcil through it — and co-defendants Nxivm president Nancy Salzman, her daughter Lauren Salzman and the cult’s bookkeeper Kathy Russell all returned to court Wednesday. Raniere did not make an appearance.

Garaufis told the court he would schedule hearings within the “next few weeks” to assess whether the fact that Bronfman is bankrolling her fellow defendants’ attorneys via a trust is a conflict of interest.

Prosecutors have raised issues with the legal fund, saying in court papers it could create questions “as to whether the attorney’s loyalties are with the client or the payor.”

Bronfman’s lawyer insists the fund was set up so her client couldn’t wield any influence.

But Garaufis has said he’s also found “issues” with the arrangement — and noted last month that the trust is rapidly running out of cash, which he worries could delay the trial.

Raniere and his co-defendants are due back in court for a hearing on Wednesday.