Ward officer Ajay Gupta had carried out construction work in the area for which a payment of Rs 70,000 was pending.
When Gupta approached Mittal, he allegedly demanded Rs 10,000 as a bribe to "clear" the bill, after which the matter was "settled" for Rs 6,000, Lokayukta's Superintendent of Police (SP) Santosh Singh Gaur told reporters.
Later, Gupta tipped-off Lokayukta officials after which Mittal was caught red-handed and arrested.
In a separate case, another GMC employee identified as Ramnarayan Bansal was caught red-handed accepting a bribe of Rs 2,000 from one Inder Bhatia for transferring the lease of a shop in his name.