The MNP facility will allow users to retain their numbers even after changing service providers.
The 100-day delay in the scheduled execution of the MNP is attributed to operators' inability to upgrade their network as well as to the delay on part of regulator Trai to come out with tariff for the service.
An official statement said, "The implementation of first phase of the MNP, in metro and category A service area has been extended to Dec 31, 2009."
The MNP service is likely to be available by end of 2009 in Delhi, Mumbai, Kolkata, Maharashtra, Gujarat, Andhra Pradesh, Tamil Nadu including Karnataka and Chennai service areas.
"The Department of Telecommunication has extended the date of implementation in view of time and efforts required to customise and upgrade the existing networks for enabling them to provide MNP service," the statement said.
It also said, "Moreover certain technical and commercial issues relating to MNP service are also to be resolved."
Department of Telecom (DoT) had issued guidelines for its implementation in the country in Aug 2008.