People for the Ethical Treatment of Animals (PETA) has written to the US Department of Agriculture demanding that it investigate accusations that elephants, giraffes and crocodiles are being neglected at the Californian estate.

Campaigners from the group say the animals have been abandoned since Jackson fled the US for the Middle East kingdom of Bahrain after beating a child sex rap in 2005.

Spokeswoman Lisa Wathne said she had seen aerial photos of the animals languishing in bleak enclosures, surrounded by pools of urine.

"These animals are in enclosures that are completely barren - it looks like a dilapidated roadside zoo," she said.

"They are deprived of everything that's natural to them. We have heard accusations that employees aren't being paid and that animals aren't being fed."

Wathne’s lobby group did not expect to hear back from the department for several months, she added.

"But we do feel that with all the accusations coming forward this is potentially a serious enough situation that there is a good chance the USDA has already looked into it, and we hope it is acting to address the situation."

In its heyday, the Neverland ranch boasted a large zoo, fairground rides and a steam railway. Last week it emerged that a veterinarian is suing Jackson for about $US90,000 in unpaid bills.

A source close to the Jackson family insisted the animals were being cared for, "perfectly well".