Amy Winehouse "headbutts" man outside pub

Amy Winehouse went out on a wild bender last night -- and ended the evening headbutting a party goer.

The troubled singer, 24, reportedly partied until 4am, and she completely lost it after arguing with a male outside a London pub, onlookers claim.

Amy "got upset and lashed out, headbutting a guy hard in the face and also punched him," said the onlooker.

"Her concerned friends rushed outside and dragged her back inside the pub."

She then headed into a sweet shop and appeared to help herself to a paper, fags and sweets before racing back to a waiting cab.

And then to Amy's surprise, she smacked her face into a lamppost.

After being dropped back at her London flat, the 24-year-old songstress infuriated one last bystander allegedly short changing the taxi driver $40, telling him his ride "wasn't worth it".

She then realized she couldn't get back into her own home as her pal had her keys and money, so she prized open her garage door to gain entry.

However, a close friend downplayed her latest relapse, insisting: "She's been working hard in the studio recording for three weeks.

"She had a studio date in Camden recording yesterday and has obviously decided to let off some steam.

"Everyone gets like that from time to time. In general she's been off everything working hard."