Anwar's comments come amid suspicion about his political future.
Speaking in a teleconference to about 5000 people in his home village from a private clinic in Germany where he is recovering from back surgery, Anwar said he was "puzzled and amused" over rumours that he would try to rejoin the United Malays National Organisation.
"I am not interested in rejoining UMNO," Anwar said. "I have never given any indication about rejoining UMNO."
The former deputy prime minister and finance minister said his priority after his release from prison two weeks ago was to push for democratic reforms and galvanise the opposition.
Anwar, 57, had earlier been careful not to rule out returning to UMNO, the path to power in Malaysia. He was the party's number two and on the fast track to becoming prime minister before falling out with then leader Mahathir Mohamad in 1998.
The prospect of Anwar joining the party caused a flurry of denunciations in the ranks, where his return could upset careers carefully built during his six-year absence.
Anwar said that "certain UMNO leaders were anxious and afraid" over his release. He has previously told the Associated Press in an interview that "the most notoriously corrupt" are vilifying him.
The door to UMNO was closed on Tuesday when the party's Supreme Council unanimously declared he was not welcomed back, though he had not even applied for new membership.
Anwar commands a huge support
base, evident upon his release
The party's annual congress of more than 2000 delegates starts on Tuesday in what should be a triumph for Prime Minister Abdullah Ahmad Badawi, whose governing coalition captured 90% of parliament's seats in March elections.
The leadership wants to take the focus off Anwar and not give him political mileage, but below the surface, delegates are expected to speculate heavily about the country's most charismatic politician.
"The delegates will most probably bring up the Anwar issue - just to send a clear message that he should not be allowed back into the party and there is no deal to bring him back," said Nur Jazlan, a leader from the southern state of Johor.
Mahathir sacked Anwar in 1998 during a power struggle amid the Asian economic crisis. The deputy was arrested after leading huge anti-Mahathir protests and subsequently convicted of sodomy and corruption.
"I am not interested in rejoining UMNO ... I have never given any indication about rejoining UMNO"
former Malaysian deputy premier
Malaysia's highest court overturned the sodomy conviction on 2 September this year, freeing him from at least five more years in prison.
But the court last week upheld the corruption conviction, which Anwar had already served, leaving him a convicted felon unable to run for office until April 2008 - 11 months before new elections must be called.
UMNO has more than 3 million members and has produced every prime minister since independence from Britain in 1957.
The party represents the interests of the dominant ethnic Malay Muslims and rules in alliance with ethnic Chinese and Indian parties.