The government on Wednesday said regulator Trai has issued show cause notices to telecom companies, including Bharti Airtel, Idea Cellular and Vodafone, for violating mobile number portability guidelines.

"Trai has received a number of complaints regarding rejection of mobile number portability (MNP) requests by mobile companies," Minister of State for Communications and IT Milind Deora told Lok Sabha in a written reply.

So far the show cause notices have been issued to "Bharti Airtel, Idea Cellular, Loop, Reliance and Vodafone", he said.

Under MNP regulations, a mobile subscriber can change service provider without changing number.

Trai has taken a number of steps to bring down porting rejections. This include a direction to all service providers simplifying format of 'Unique Porting Code' to minimise errors in the process of placing Mobile Number Portability (MNP) request to the recipient operator so as to minimise the MNP rejections, Deora said.

Further, based on sample of MNP rejection and the complaints received in Trai, the regulator analysed the genuineness of rejections based on information received from MNP service providers and concerned service providers.

Wherever violation of MNP regulations and directions observed, Trai issued show cause notices to the concerned service providers, he said.

On May 24, Trai had issued broad directions on contractual obligation which says telecom operators should not reject MNP request if the amount of subscriber due is less than Rs 10.

It also said that MNP request can be rejected if the customer has post-paid connection with bundled handset and the subscriber has not complied with the exit condition of the deal.