The line-up of reformed rock legends Led Zeppelin could be in doubt - they are reportedly looking to replace singer Robert Plant.

The rockers reunited for an historic gig last year - and rumors of a full world tour have dogged the band ever since.

Frontman Plant attempted to end the speculation by hitting the road with country star Alison Krauss.

But the rest of the group have reportedly been rehearsing with stand-in singers - and are now said to be considering replacing Plant altogether.

A source tells British newspaper The Sun, "They've been rehearsing frequently in London and the band is really gelling. There's an American guy who has been standing in for Robert regularly and doing a great job.

"Obviously they want the original frontman to join them on the road but he still won't commit. They will be finalization plans for shows over the next couple of months and will tell Robert that if he doesn't want to be involved they will go ahead without him."

(This news article provided by World Entertainment News Network)