"If we assume that the elections are fair and free and that the people say no to us, then I may (resign). In fact, I am in communication with some universities already. But now I have a duty. They robbed us of our elections and I want to present the case on behalf of Malaysians," said Anwar, 65.
"In a faulty and fraudulent election, I now will continue the fight to defend all Malaysians," said the leader of three-party Pakatan Rakyat (People's Pact) alliance.
Anwar had earlier stated that he would step down from politics if his alliance did not win in the general elections.
Prime Minister Najib Razak-led Barisan Nasional (National Front) coalition retained its 56-year grip on power in the one of the country's most hotly contested parliamentary votes, marred by allegation of widespread vote-rigging.
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The National Front won 133 of Parliament's 222 seats, down slightly from the previous 135.
Najib was sworn in as Prime Minister yesterday.
Anwar said the opposition alliance was looking at alleged irregularities found in 29 to 31 seats, but remained non-committal in filing a formal election petition on it.
Yesterday, Lim Kit Siang of opposition DAP supported Anwar as the parliamentary Opposition Leader.
His comment came after Anwar said he was willing to give up the Opposition Leader's post to Lim, as DAP was the biggest block in the pact with 38 parliamentary seats.
However, Lim rejected the offer.
Anwar assumed the position after the Permatang Pauh by-election in 2008.
After Sunday's general elections, Anwar's party PKR has 30 seats and PAS 21 seats.
"DAP has done very well, especially in Gelang Patah, where the win was unexpected," he said.
However, party adviser Lim Kit said the party would file an election petition to reject the results in areas where it had lost by small margins.