Raila said there will be no point for Wiper Party leader Kalonzo Musyoka, Narc-Kenya leader Martha Karua, DAP-K leader Eugene Wamalwa or Roots Party's George Wajackoya taking part in a process presided over by a commission they do not trust.
The leaders later met with Catholic bishops as talks to end the stalemate between Raila and President William Ruto began.
"We have had a very fruitful and productive conversation. They have raised issues which are of concern to Kenyans, the church and politicians," said Raila. "We are very happy and pleased with the role the church is playing."
Among those in attendance included archbishops Philip Anyolo (Nairobi), Martin Kivuva (Mombasa), Anthony Muheria (Nyeri), and bishops John Obala (Ngong) and Dominic Kimengich (Eldoret), among others.
Archbishop Kivuva said they deliberated on the peaceful co-existence of Kenyans.
"It is clear that the talks have begun and we will involve everyone. We urge Kenyans to maintain peace," Kivuva said. "It is possible to get this country where it was. We are doing well, but we can do better."
The Mombasa archbishop urged security agencies to guarantee peaceful protests. This comes amid sustained pressure on Inspector General of Police Japhet Koome over the brutality meted against demonstrators by the police.
"As Catholics, we have our processions on Palm Sunday. The demonstrations must be as peaceful to allow others to conduct their day-to-day affairs. The police should respect the demonstrators and allow them to march in peace," he said.
In the earlier meeting in Kibera, Raila criticised Ruto for discussing current happenings while abroad instead of tackling them here. He claimed this was a strategy to hoodwink the international community.
The former PM said they have asked the President to lower the cost of living, have an all-inclusive process in the formation of Independent Electoral and Boundaries Commission, and include all communities in government appointments which he has failed to do so far.
Raila asked Ruto to stop buying opposition MPs, saying this is a sign that he did not win the last election. He challenged legislators who are not happy with being in Azimio coalition to resign and seek fresh mandate from the people.