Omisore is believed to be shopping for a new party to contest the state's gubernatorial election.
This is believed to be in reaction to the loss of his faction at the party's March 25 congress in Osun State which heralded the victory of Soji Adagunodo as the substantive Chairman of the party in the state.
The Deputy National Publicity Secretary of the PDP, Diran Odeyemi, said Omisore was making a wrong decision.
He said, "It is unfortunate that Otunba (Omisore) is making a wrong political decision. He should have learnt from those who left PDP and came back. In politics, you don't win all the time.
"So, if he does not have his way this time around, it does not mean he cannot make his way some other time."
Omisore is believed to be consulting widely on the new political party he could use to realise his gubernatorial ambition in the state's September 2018 election. The Social Democratic Party (SDP) is rumoured to be a possible destination for him.
While contesting on the platform of the PDP, he lost the 2014 gubernatorial race to incumbent, Rauf Aregbesola, who is approaching the end of his second term in office.
The 60-year-old businessman and politician served as Deputy Governor of Osun State from 1999 and 2003, and went on to represent Osun East senatorial district in the Nigerian Senate between 2003 and 2009.