Lily Allen has likened herself to a shorter and “considerably” less sexy Charlize Theron.

The pop star says the insomnia she is suffering due to jetlag has started to send her crazy. Lily joked having no sleep is turning her into a character similar to the one played by Charlize in her dark comedy film Young Adult. Charlize portrayed Mavis Gary, a self-absorbed and psychotic former high School 'It Girl' who turned into an alcoholic divorcee.

"Jetlag is turning me sour. I'm becoming more and more like Charlize Theron in Young Adult as the days go by," Lily tweeted. "...With less height and considerably less sex appeal (sic)."

The outspoken singer has been talking about her insomnia for the last few days after returning to the UK from Los Angeles. The British singer jetted to the US to perform at a secret show with Pink whom she collaborated with on the American artist’s new track True Love.

Lily "really enjoyed" the experience of singing on stage again. This follows her famous announcement she was quitting the music industry in 2009.

Lily, who is five months pregnant with her second child with husband Sam Cooper, was supported by friends and family at the secret show. Also in attendance supporting her mum was Lily's eight-month-old daughter Ethel.