The 67-year-old Muslim cleric, who was convicted for playing a role in the 2002 Bali bombings that killed 202 people, responded to the news by lashing out at Australia, accusing it of interfering in Indonesia's judicial process, a supporter said.
Indonesia traditionally cuts prison terms on national holidays - usually by several months - for inmates who exhibit good behaviour, including convicted terrorists. Only those sentenced to death or life in prison are excluded.
Prison wardens had asked that Bashir, who was sentenced in May to 30 months behind bars, have a month taken off his jail time, but Justice Minister Hamid Awaluddin said the request was denied.
"No. He did not get it," Awaluddin repeatedly told reporters after performing morning prayers on Thursday, the first day of Eid al-Fitr, the holiday marking the end of Ramadan.
He refused to comment further.
Authorities also requested sentence reductions for 27 other convicted Bali bombers, and an announcement was expected later on Thursday on whether any of those had been granted.
"Bashir condemned the Australian government for intervening in Indonesia's legal affairs"
member of an Islamic group
Bashir already benefited from a 4 1/2 month remission earlier this year and is scheduled to walk free from the Cipinang Prison in Jakarta in June.
Australia, home to 88 of the Bali bombing victims, has repeatedly said the Muslim cleric's original sentence was already too light and should not be cut further.
"Bashir condemned the Australian government for intervening in Indonesia's legal affairs," said Fauzan al-Ansoria, a member of Majelis Mujahidin Indonesia, an Islamic group founded by Bashir.
But he also called on his supporters to accept the government's decision, al-Ansori said after meeting Bashir in jail.
Bashir is alleged to be the spiritual leader of the Jemaah Islamiyah, which is suspected in several other deadly attacks in Indonesia, including the 2003 J.W. Marriott hotel bombing that killed 12 people, and the September 2004 Australian Embassy bombing that killed 11.