A charity that helped organize last year's star-packed Concert for Sandy Relief says millions of dollars in donations were left on the table due to spotty service from the company tasked with processing the donations.

In a lawsuit filed Wednesday in Los Angeles superior court, the Robin Hood Foundation alleges Patriot Communications failed to "perform the core services it contracted to provide," which led to "virtually a complete blackout, during a prime portion of the event."

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According to the suit, Patriot's donations website could be accessed only "intermittently" between 8:30 p.m. and 10 p.m. the night of the concert, and lost "virtually all functionality" from approximately 10:06 p.m. to 11:06 p.m. The suit says Patriot processed less than $15,000 in donations during that hour long blackout, despite having processed roughly $2 million in the previous hour.

Robin Hood alleges Patriot aggressively presented itself as the only company capable of handling the large volume of phone calls and Internet donations that would come during the concert, and exaggerated its ability to provide adequate service.

"The event eventually raised many millions of dollars for this worthy cause, but it would have raised millions more had the efforts of many potential donors not been stymied by Patriot's gross failure," the lawsuit reads.

Robin Hood says it paid patriot more than $1.4 million for its services, including an additional $750,000 to ensure "adequate resources" would be allocated for the event.

The charity says after the concert, Patriot presented it with an invoice seeking an additional sum of more than $410,000 for "donor services and residual activity." Robin Hood maintains donations it missed out on during the blackout should make up for that cost.

Robin Hood is suing for breach of contract, breach of warranty, negligence and fraud. It seeks damages of at least $5 million.

The Concert for Sandy Relief, held Dec. 12, 2012 at Madison Square Garden, featured dozens of A-listers, including  Kanye  West, Alicia Keys, Paul McCartney, The Who, Eric Clapton, Roger Waters, Bruce Springsteen and the E Street Band, Billy Joel, Bon Jovi, Eddie Vedder and  Dave Grohl. It raised more than $50 million.

Robin Hood is represented by Gibson, Dunn & Crutcher.

Patriot did not immediately respond to request for comment.