A urgent investigation is under way to explore links between travellers pleading to stay in illegally-built homes in south Essex and "millionaire" mansions in Ireland.

The Basildon Council probe follows the publication of a book suggesting Dale Farm, in Oak Lane, Crays Hill, was set up by traveller traders from Rathkeale, in County Limerick, who own a £350million empire of properties in the town described as the "spiritual home" of Crays Hill's Sheridan clan.

The Outsiders: Exposing the Secretive World of Ireland's Travellers, by Irish journalist Eamon Dillon, describes Dale Farm as an "unofficial halting site" for the wealthy entrepreneurs.

It claims their Irish homes are deserted for months while owners trade in Europe and the UK, using Dale Farm and the Smithy Fen site, at Cottenham in Cambridgeshire, as bases.

The claim flies in the face of arguments voiced during years of legal tussles with Basildon Council that Dale Farm served as a vital permanent home for the sick, elderly and children who needed schooling.

Crime reporter Dillon, of leading Irish tabloid, the Sunday World, spent ten years investigating travellers in Ireland.

He says the Rathkeale clan trades in Polish furniture, antiques and foreign cars, as well as running asphalt businesses like those based at Dale Farm.

He says it created a network of temporary sites in Ireland and the UK, following changes in Irish law, which have clamped down hard on roadside camping.

Basildon Council leader Malcolm Buckley said the book and this week's Echo revelations that travellers owned land across the UK would be sent to Secretary of State for Local Government Ruth Kelly, who is due to decide the fate of Dale Farm next month.

The book, discovered by Oak Road campaigner Len Gridley when he took part in an Irish TV talk show, identifies some of the wealthiest Rathkealers - said to be worth as much as £24million.

Mr Buckley said: "This book, coupled with the Echo's investigations, casts serious doubts on the legitimacy of the Dale Farm occupants' claims.

"I will be reading it in great detail. Legal advisors will also see how it may affect the appeals.

"At first glance, there are many connections between people described in the book and people living in the district, and indeed there do appear to be some familiar faces in its photographs. I will be interested to hear what the author has to say about the connections to Dale Farm in particular."