The FIR was registered against Amanmani Tripathi and his four aides on the complaint of contractor R K Pandey at the Cant police station yesterday, a police spokesman said here.
Pandey alleged that Tripathi abducted him yesterday after intercepting his car.
"I was tortured and extortion money was demanded from me," he said.
He was later allowed to go.
Amanmani is the son of Amarmani Tripathi, who is in jail in the murder case of poetess Madhumita Shukla.