The man had complained to the East Delhi Municipal Corporation against an alleged illegal construction going on in the area.
CBI sources said the people allegedly involved in the illegal constructions had approached Vijay Kumar, who was the sub-inspector of the area, to put pressure on the complainant to withdraw it.
It is alleged that the people who were doing the construction had attacked the complainant in his house when he called Delhi Police on 100 number.
The complainant has alleged that Kumar demanded Rs five lakh from him and asked him to withdraw his complaints to the civic body and the police.
"After negotiation with the complainant, the SI allegedly settled for a bribe of Rs 2 lakh. The sub-inspector had also allegedly put pressure on the complainant to withdraw his complaint to the Delhi Police," CBI spokesperson R K Gaur said.
He said CBI laid a trap and caught the sub-inspector, posted at Krishna Nagar police station, red-handed while accepting a bribe of Rs 1.20 from the complainant.