In November, the country had 921.47 million telecom subscribers.
"Total wireless subscriber base decreased from 890.60 million in November 2012 to 864.72 million at the end of December 2012.
This decline is majorly due to large scale disconnections of inactive SIMs by some of the service providers," Telecom Regulatory Authority of India (TRAI) said in a statement.
With this, the overall teledensity (connections per 100 people) in India decreased to 73.34 percent at the end of December, 2012 from 75.55 per cent in the previous month.
All operators lost users in December 2012, barring Unitech, HFCL and BSNL, which together added 995,554 users.
Reliance Communications lost the largest number of users - 15.58 million - taking its user base to 118.52 million at the end of December.
It was followed by Vodafone, which lost 3.28 million users. RCom user base now stands at 147.47 million users.
Tata Teleservices lost 2.95 million subscribers (now at 69.55 million), Aircel 1.97 million (63.34 million) and Bharti Airtel 1.7 million (181.90 million).
Idea Cellular lost 197,231 users, taking its subscriber base to 113.9 million at the end of December, 2012.
CDMA player Sistema Shyam lost 789,420 users and it now has a user base of 14.88 million.
State-run BSNL added 13,013 users, taking its subscriber base to 99.92 million, while MTNL lost 2,975 users and its user base now stands at 5.3 million.
By the end of December 2012, about 80.06 million subscribers had submitted their requests for porting their mobile numbers.
In MNP Zone-I (Northern and Western India), maximum number of requests have been received in Rajasthan (7.59 million), followed by Gujarat (6.94 million).
In MNP Zone-II (Southern and Eastern), maximum number of requests have been received in Karnataka (9.90 million),
followed by Andhra Pradesh Service area (7.40 million). In all, 2.94 million subscribers submitted requests for MNP in December.
Wireline subscriber base declined from 30.87 million in November to 30.79 million at the end of December, TRAI said.
Total broadband subscriber base has increased from 14.88 million in November to 14.98 million at the end of December, a growth of 0.67 percent.