"No. Hashem Abedi will not be extradited," Ahmed Ben Salem, spokesman for the "Deterrence Force" which acts as the police of the UN-backed unity government in Tripoli, told AFP.
Yesterday, British police investigating the May bombing that killed 22 people had requested the extradition of the attacker's brother from Libya.
Salman Abedi detonated a suicide bomb after a concert by pop star Ariana Grande, in Britain's worst terror attack in more than a decade.
But Ben Salem said Libya had no extradition accord with Britain, and that "the Abadi affair is with the attorney general's office which is in charge of the investigation".
According to the Deterrence Force, Hashem Abadi has admitted to having been in Britain at the time of preparations for the attack and that he was "fully aware of the details of the terrorist operation".