In an interview with the BBC's Newsday programme, Atiku Abubakar denied that he joined the APC so that he could run for president in 2015. He also said he would never come back to the PDP.
Atiku Abubakar, a former Vice President of Nigeria, announced his decision to leave the PDP on Sunday.
BBC Nigeria analyst Aliyu Tanko called Atiku the most significant national politician to defect from the PDP to the APC.
Atiku maintained that he did not join the opposition party so that he could contest presidential elections but to enhance APS'c development and ensure that good governance is entrenched in Nigeria.
The former VP also said he believed that Nigeria should have a two-party political system.
"I really want to see a strong second party for the party," he said.
Atiku pledged that he would never return to the PDP, saying that from all indications the party would no longer be what it used to be.