US Federal Communications Commission Chairman Ajit Pai (pictured) criticised US operators for falling behind in an ongoing campaign to combat nuisance calls and warned they could face action from the agency if they fail to implement a new call authentication mechanism by 2019.

In letters to the CEOs of Verizon, AT&T, T-Mobile US, Sprint, US Cellular, Comcast, and Charter, Pai pressed the companies to quickly adopt a spam prevention framework known as SHAKEN/STIR, which requires operators to validate call traffic as legitimate before it is passed along to a consumer.

The method is meant to block scammers from using false caller ID information to reach potential victims and makes it easier to trace the origin of spam calls.

Operators including AT&T, Verizon and T-Mobile have committed to implement the system, but have not yet rolled it out. Pai sought an update on their deployment plans and called on stragglers which are still to pledge to use the new system to get moving.

He set a deadline for operators to deploy the technology during 2019, adding “if it does not appear that this system is on track to get up and running next year, then we will take action to make sure that it does”.

The push is part of the FCC’s ongoing effort to fight the billions of nuisance calls US consumers receive every year, a campaign Pai previously called his “number one consumer protection priority”.

In 2016, the Commission oversaw the creation of the Robocall Strike Force, a coalition of operator and industry partners tasked with developing best practices to detect, prevent and filter such calls. The following year, the FCC opened an inquiry which resulted in the creation of the SHAKEN/STIR framework, and also passed new rules allowing operators to block calls originating from fraudulent numbers.