Nyan Win, the NLD spokesman, welcomed the release of Win Tin and announced that three more of their members had been freed on Tuesday.
The party won a landslide victory in elections in 1990 but the military refused to acknowledge the result, instead stepping up arrests and repression of dissidents.
The state-run New Light of Myanmar newspaper said in a report earlier on Tuesday that that 9,002 prisoners would be released due to good conduct and "to enable them to serve the interests of the regions and their own and the fair election to be held in 2010".
"Plans are being made for those serving prison terms to turn them into citizens to be able to participate in building a new nation," it said.
The military government which rules Myanmar has said the country will hold multi-party elections in 2010 as part of its so-called roadmap to democracy, but critics say the polls are just a way for the generals to legitimise their control.
Win Tin said he had complained to prison officials about being included in the nationwide amnesty.
"I did not accept their terms for the amnesty. I refused to be one of 9,002," he said.
Win Tin said that no conditions had been attached to his release.
"Far from it. They should have released me five years ago. They owe me a few years," he said.
The announcement came just days before the first anniversary of massive protests against military, which were crushed by the government leaving at least 31 people dead.
|Win Tin spent 19 years in Yangon's Insein prison [File: EPA]
Human rights groups say that about 700 of the 2,000 political prisoners were detained during last September's demonstrations.
The government denies there are any political prisoners in Myanmar's jails saying that have all committed some type of crime.
The UN and human-rights groups have repeatedly called for the release of Win Tin, who Amnesty International says has been sentenced three times to a total of 20 years imprisonment.
In March 2006, Win Tin was sentenced to seven years in jail for communicating with the UN about prison conditions and for writing and circulating articles in prison. Authorities characterised this as "secretly publishing propaganda to incite riots in jail".
The letter to the UN was reported to have been titled "The testimonials of prisoners of conscience from Insein Prison who have been Unjustly Imprisoned, Demands and Requests regarding Human Rights Violations in Burma" and detailed a lack of medical treatment and torture in prison.