Verizon pulled out after footage of rap artist Akon dancing provocatively on stage with a girl - reportedly in her teens - was posted on the internet.

The incident did not take place during one of Stefani's concerts.

Billboard magazine quoted Stefani's management as saying they were "surprised and shocked" by the move.

Eric Rabe of Verizon, a telecommunications company, told the BBC News website: "We had already agreed to sponsor the Stefani tour when Akon was brought in and we have kept that situation under review.

"We have now decided to withdraw and the video was part of that decision."

So far no concerts have been cancelled and Akon remains on the tour.

While refusing to discuss the exact amounts involved, Stefani's manager Jim Guerinot was quoted as saying "we're just in the beginning stages of evaluating" the financial impact.