Lindsay Lohan Duets with the Ronsons

Lindsay Lohan has performed a duet with her girlfriend Samantha Ronson and the DJ's producer brother Mark - taking the stage at a family celebration in London.

The actress/singer attended a Jewish Bar Mitzvah ceremony for one of Ronson's relatives at a synagogue in the British capital on Saturday.

The family went on to celebrate the occasion with a party at the Mandarin Oriental hotel, in London's Knightsbridge.

And Lohan delighted guests by taking to the stage at the event to sing with her lover, performing the Beatles' With A Little Help From My Friends.

The girls were joined by Ronson's older brother, Mark, who accompanied them on guitar.

A source tells British newspaper The Sun, "It was amazing. Everybody loved it. Lindsay and Sam looked really loved up."