The veteran CPI-M leader and Leader of Opposition in the state assembly, in a letter to Modi, said the Central Vigilance Commission should probe the allegations against E.K. Bharath Bhushan.
He alleged that Bhushan has a soft corner for real estate developers in the state.
In the letter, Achuthanandan said the chief secretary appears to have the full support of Chief Minister Oommen Chandy.
"Since you (Modi) are the minister of personnel, I request you to order a probe into the chief secretary's land deals and also that has taken place in the name of his wife," Achuthanandan wrote in the letter.