The Sirisena-led government, which had ousted Rajapaksa in the 2015 presidential elections in the island nation, has entered into joint venture agreements with Chinese firms to built a seaport and an industrial park around it in Hambantota district.
The Lankan government is also in talks with the Airport Authority of India (AAI) to set up a joint venture for managing the Mattala international airport, which is named after Rajapaksa and dubbed as the world's emptiest airport.
The Opposition has opposed both the deals, terming them as sell-out of national assets to foreigners.
However, the government stressed that the joint ventures are on long term lease arrangement and not outright sale.
Addressing a protest rally in Colombo on Thursday, Rajapaksa warned the foreign partners, "Please do not buy anything (state ventures) sold by this government. I will have to reconsider them when I return to power."
He was referring to Lanka's debt equity share ventures with China to run the southern port of Hambantota.
Rajapaksa's Sri Lanka People's Party (SLPP) had made remarkable political gains in the February local election, winning more than two thirds of the councils. Since then he has been demanding a snap parliamentary poll, which he says his party will surely win.
The parliamentary polls in Lanka are due in 2020.