India to have mobile number portability from Dec 31

* MNP in metro cities and lucrative zones from Dec. 31

* To be extended to rest of India by March 20, 2010

* Porting charges must not exceed 40 U.S. cents - regulator

NEW DELHI, Nov 20 (Reuters) - India will introduce mobile number portability on Dec 31, a move that could further intensify the stiff competition in the world's fastest-growing wireless market and push call charges lower.

Mobile Number Portability (MNP), which allows users to retain their number even if they switch operators, will be introduced in two phases, the telecoms regulator said, first in the metro cities and the so-called Category A telecom zones and in other areas by March 20.

MNP helps in "increasing competition between the service providers and acts as a catalyst for the service providers to improve their quality of service," the Telecom Regulatory Authority of India (TRAI) said on its website.

The regulator also notified certain charges associated with MNP and said switching charges for users must not exceed 19 rupees (U.S. 40 cents).

For the TRAI order, see link.reuters.com/pej72g

Four new firms including ventures of international telecom operators Telenor (TEL.OL: Quote, Profile, Research), Etisalat ETEL.AD and Batelco BTEL.BH are set to start services in India this year and MNP would make it easy for them to lure existing subscribers.

For more Reuters stories on Indian telecoms, click on [LEN-RTRS-IN-TEL]. ($1=46.6 rupees) (Reporting by Devidutta Tripathy; Editing by Malini Menon)