Sir Paul McCartney has added his star power to Tony Bennett's anti-gun violence campaign and called on fans to lobby U.S. representatives to push for tighter firearms laws following the tragic Newtown, Connecticut school massacre in December (12). The Beatles legend has recorded a phone message for Bennett's Voices Against Violence initiative in the hope of encouraging devotees to send a text, which will connect them to the superstar's special voicemail and put them through to their local Senate office to express their opinions over the need for more gun legislation. McCartney's efforts to boost the campaign's profile, which is also backed by actor Alec Baldwin and singers Gloria Estefan, Josh Groban and Juanes, comes as officials in the U.S. Senate are due to vote on Wednesday (17Apr13) on whether to approve a proposal to expand background checks for firearms sales. Twenty children and six adults were killed at Newtown's Sandy Hook Elementary School last year (12) when a gunman opened fire inside the education facility. The tragedy was the latest to rock America in recent years, following shootings at Colorado's Columbine High School in 1999, Virginia Polytechnic Institute and State University in 2007, and a movie theatre in Aurora, Colorado in July (12).