Lady Gaga was honoured to meet Liza Minnelli for the first time after her concert this week at New York's Madison Square Gardens - and gave her a special shout-out during the show.

The Born This Way singer sent the Cabaret star tickets to the show, which was filmed for HBO, and Liza joined her backstage quickly before the show, The New York Post reported.

Lady Gaga made an apparent dig at Britney Spears during her performance, telling the audience: "I do not lip-synch. I'm not going to waste your time watching some b***h lip-synch her way through an HBO special."

She then gave a shout out to her special guest adding: "Especially not with Liza watching."

The 24-year-old Grammy winner - real name Stefani Germanotta - has also had Beatle Sir Paul McCartney in the audience during her newly launched Monster Ball tour.

Meanwhile, Lady Gaga is no longer the most popular person alive on Facebook after Eminem knocked her off the top spot.

The rapper now has almost 29 million fans on the social networking site edging just ahead of Gaga, who has been number one for eight months, by just under a million.