One of Britain’s most powerful politicians wasn’t afraid to phone Jeffery Epstein looking for a favor — even while the pedophile was behind bars for sex crimes, according to a new documentary.

A new “Dispatches” documentary set to air on Britain’s Channel 4 Monday claims Lord Peter Mandelson was Labour Business Secretary in 2009 when he called Epstein — then cooling his heels in a Florida jail after pleading to procuring an underage prostitute — trying to arrange a meeting with the boss of JP Morgan bank, according to The Sun.

The pedo and the politician were seemingly so close that Epstein even had a pet name for the UK cabinet member — calling him “Petie,” according to the report.

“I must say I was astonished that a British Cabinet minister at that time, probably the most powerful man other than the Prime Minister, was calling Jeffrey in jail,” a friend of Epstein’s who revealed the call told the documentary, according to The Sun.

The politician — who had also been Tony Blair’s spin doctor — is one of the powerful figures mentioned in the upcoming TV special, “The Prince and the Paedophile,” which focuses on Epstein’s close ties with Britain’s Prince Andrew.

The friend told the documentary crew that he was visiting Epstein when he got the call.

“While I was there, he (Epstein) received a call and said, ‘Hello, Petie.’ And Petie wanted to meet Jamie Dimon of JP Morgan. He said, ‘Yes, I’ll sort it out’.

“Petie turned out to be Secretary of the Board of Trade, Peter Mandelson,” he insisted, according to The Sun.

Lord Mandelson, 65, has previously been photographed shopping with Epstein, who killed himself in his Manhattan lockup this summer as he faced federal sex-trafficking charges.

“Our client has no recollection of a telephone conversation with Mr Epstein in January 2009,” lawyers for Mandelson, who now sits in the UK’s House of Lords upper parliament, told The Sun.

“He talked to bank CEOs on a regular basis, including Mr. Dimon. These contacts were arranged through his office.”