Pramod Mahajan's son Rahul is in a critical condition

Vivek Maitra was an aide of Pramod Mahajan, who was shot dead last month.

He died of alleged food poisoning early on Friday.

The politician's son, Rahul Mahajan, was admitted to hospital with similar symptoms on Friday morning and is in a critical condition.

'White powder'

Reports say Mr Maitra and Rahul Mahajan were admitted to Delhi's Apollo hospital after a late night dinner.

A hospital spokesperson said: "Initial examinations shows that the death of Vivek Maitra and the ill health condition of Mahajan is due to food poisoning."

Pramod Mahajan was an influential BJP leader

It is unclear what caused the apparent poisoning.

Senior Delhi police official Manish Agarwal told reporters that doctors had "seized some white powder" from the "possession" of Mr Maitra and Rahul Mahajan when they were brought to the hospital.

"We have been told that they had champagne. Their servants are saying that three people visited them at night. The doctors are saying it is [an] unknown poisoning," he said.

Pramod Mahajan, a former federal minister, died last month, 12 days after being shot, allegedly by his brother.

Pramod Mahajan was an influential leader in the BJP and correspondents say he was seen by some as a possible future candidate for prime minister.