
Under the scheme, which is expected to be discussed by the Cabinet this week, 4,000 public buses would be leased by the government at a relatively high rental fee plus a hefty daily maintenance fee, totalling Bt67 billion over a 10-year period.
Pridiyathorn and other critics have suggested the scheme had been devised by a group of politicians to exploit public funds.
"This plan should be ended because data suggests there are hidden benefits [for politicians]," the former central bank chief said.
However, Piyapan Jampasut, chairman of the Bangkok Mass Transit Authority (BMTA) board insisted the deal was the best way to reorganise the money-losing BMTA, which runs the city's bus services.
The BMTA would not have to shoulder the maintenance costs throughout the 10-year lease period, he said, adding that the bus rental fee of Bt4,657 per day per bus was reasonable.
The BMTA's accumulated losses amount to Bt70 billion.
Interior Minister and Bhum Jai Thai Party leader Chaovarat Charnweerakul brushed aside allegations the project would benefit certain individuals.
"The Bt30 daily ticket for all routes per person is cheap. We are doing our best with a project that was initiated by the previous government. I insist there are no extra benefits going to any party," he said.
He noted that if there was collusion among bidders, the project would not be submitted for Cabinet approval as sought by Deputy Interior Minister Boonjong Wongtrairat, the right-hand man of Newin Chidchob who forms a major faction within Bhum Jai Thai.
Chaovarat said the Democrat Party, which heads the government, must have a good reason for wanting to end the project.
Politically, the row over the scheme could widen the rift between Bhum Jai Thai and the Democrats.
Other simmering conflicts between the parties include rice and corn pledging programmes as well as the land-leasing project for agricultural purposes.
While the Democrats tighten scrutiny for Bhum Jai Thai's pledging programmes, the latter, led by Newin's brother Saksayam, argued against a plan put forward by Democrat MP, Thaworn Senneam, a deputy interior minister, to lease land for agricultural purposes.