Amy Winehouse opens European tour with “worst ever” concert (VIDEO)

Amy Winehouse has canceled her next leg of her European tour, after an opening gig described as "the worst concert in the history of Belgrade."

Winehouse turned up an hour late, frequently stumbled on stage (and was ultimately booed off it) and frequently fell behind in her songs, Reuters reports.

To make matters worse, she addressed the disgruntled crowd of 20,000 by saying, "Hello, Athens," according to MTV.

One Belgrade fan, writing on Winehouse's website, described her as "another punkass junkie and lush."

Winehouse, 27 — who became an overnight sensation with her 2006 hit single "Rehab" but subsequently fell from grace "crippled by substance abuse problems" — has canceled appearances this week in both Athens and Istanbul.

A statement from her spokesperson reportedly read:

"Despite feeling sure that she wanted to fulfill these commitments, she has agreed with management that she cannot perform to the best of her ability and will return home.

She would like to apologize to fans expecting to see her at the shows but feels that this is the right thing to do."

Her next scheduled show is July 8 in Spain.

Winehouse's show came just weeks after she entered an alcohol rehab program at the Priory Clinic, according to People. Alcohol had reportedly been banned from the current 12-date tour.

Winehouse, who won four Grammy awards in 2008 including best new artist and album of the year, has reportedly been working on the follow-up to breakthrough album "Back to Black."