A lead actress in Broadway's Spider-Man: Turn Off the Dark officially walked away from the long-delayed musical, another blow for an unsettled production that has already sent several actors to hospital and burned through millions of dollars even before its official opening.

Natalie Mendoza, who had recently returned to the stunt-heavy show after suffering a concussion during its first preview performance last month, pulled out for good following several days of negotiations between lawyers for both sides.

Producers broke the news to the cast before the Thursday evening performance.

The actress cited her head injury as the reason she walked away.

"It has been a difficult decision to make, but I regret that I am unable to continue on Spider-Man as I recover from my injury," Mendoza said in a statement.

The protracted exit of a key star only a few weeks before the launch of what is considered Broadway's most expensive show was in keeping with a production that has been marred by accidents and bad press.

Mendoza played Spider-Man's evil love interest Arachne - a part written by director and co-book author Julie Taymor - and is one of four actors to be injured in the 65 million US dollar musical that has been delayed four times this year alone.

Mendoza's move comes 10 days after stuntman Christopher W. Tierney, playing the web-slinger, fell about 30 feet into a stage pit when a safety tether failed on December 20.

He spent Christmas in hospital while recovering from back surgery and was transferred to a New York City rehab facility this week. His accident was also the last night Mendoza performed as Arachne.

The drip-drip of almost weekly bad news has turned the musical - whose costs easily dwarf Broadway's last costliest show, the 25 million US dollar Shrek the Musical - into fodder for late-night comics, with both Conan O'Brien and Saturday Night Live spoofing the show.

Even Donny and Marie Osmond are ridiculing it in their own Christmas musical.