Azimio lawmakers have alleged that senior Kenya Kwanza are lining up to buy state corporations tipped for sale.
The opposition further claimed that those behind the plot have struck deals in foreign countries concerning the sale.
Led by Minority Leader Opiyo Wandayi, the leaders cited Mombasa and Lamu ports as among strategic assets up for sale.
"We repeat that the proposed sale of parastatals is not meant to revive the institutions. It is meant to help people in Kenya Kwanza who have formed companies in Asia, the Middle East and Eastern Europe," said Wandayi in a joint statement.
Opiyo said the plot to bypass Parliament in the Privatisation is suspect and vowed to oppose it.
The opposition team also listed several hotels including Bomas of Kenya as among those being set up for the sale.
The leaders said they will mount opposition to the bills approved by Cabinet setting stage for the sale.
"Law change will give National Treasury unchecked power to sell institutions," the leaders said.
"There is no way Ruto is going to convince Kenyans that he is acting in the best interest of the nation by selling assets without involving representatives of the people in Parliament."
They held that Azimio doesn't support the move, pointing out they took a similar stand when President Kenyatta's team sought to sell sugar firms unprocedurally.
The leaders spoke a day after the Cabinet approved the Privatisation Bill that allows Treasury to sell public corporation without Parliament's nod.