The Barbarians' preparations for this weekend's eagerly-anticipated clash with world champions South Africa have been thrown into chaos with captain Mark Regan and fellow Premiership star Andrew Sheridan banned from taking part.

Premiership sides Bristol and Sale have both ruled their respective players out from Saturday's fixture that clashes with the final round of matches in this season's EDF Energy Anglo-Welsh Cup.

Bristol coach Richard Hill told The Guardian newspaper, "As far as we are concerned, Mark will not be involved in the South Africa match.

"He has received a letter from the club to that effect and we have taken a very strong line over this."

Bristol chief executive David White told BBC Sport: ``Premier Rugby have made their decision and we are supporting that.

``We have not released him, he can't play and we have the jurisdiction to fine him.

``If he does play he'll be breaking his contract and will have to face the consequences.''

Sale too moved quickly to rule Sheridan out of the game after he was announced in the Barbarians squad yesterday.

A statement released by the club read, "The news that Andrew Sheridan has been named in the Barbarians Squad to play against South Africa at the weekend is incorrect.

"Andrew is currently in training with his Sale Sharks team mates, preparing for Friday evening's EDF Energy Cup game at Leicester Tigers."

However, Sheridan's agent Mike Burton has insisted that the England international prop is free to play in the game as it was a clause in his recently signed contract.

Burton, who is also a member of the Barbarians' committee, commented, "The new contract he [Sheridan] signed with the club last week contained an unconditional clause that allows him to play for the Barbarians against South Africa on Saturday.

"Clearly Sale are in breach of that contract. I will be speaking to Andrew to get his views on the matter. Any decision will be his and his alone."

Premier Rugby have taken a firm stance on the release of players insisting, "the decision not to release players for the Barbarians was made at a meeting of all 12 Premiership clubs and it was a unanimous one."

The newspaper reports that the clubs would face a financial sanction if the players turn out for the Barbarians.

"We want to work with the Barbarians and will provide players for their end-of- season game against England and their summer tours," said the PRL chief executive, Mark McCafferty. "The autumn international window is another matter."

A similar row looms for those Magners Celtic League players slated to appear at Twickenham.

Cardiff Blues stars Martyn Williams and Tom Shanklin have also been named in the Barbarians squad even though both are expected to feature in their Anglo-Welsh clash with Bath on Friday night.

Similarly Ospreys scrum half Justin Marshall is also slated for the Twickenham fixture that clashes with the Welsh side's meeting with Harlequins on Sunday afternoon and Munster's Federico Pucciarello would be expected to feature against Leinster in the Magners League on Friday night.

Barbarians Squad:

Backs
Jason Robinson (England & British Isles)
Joe Rokocoko (Blues & New Zealand)
Isoa Neivua (Warriors & Fiji)
Ben Cohen (England & British Isles)
Conrad Smith (Hurricanes & New Zealand)
Tom Shanklin (Cardiff Blues, Wales & British Isles)
Ma'a Nonu (Hurricanes & New Zealand)
Matt Giteau (Western Force & Australia)
Peter Grant (Stormers)
Justin Marshall (Ospreys & New Zealand)

Forwards
Andrew Sheridan (Sale Sharks, England & British Isles)
Federico Pucciarello (Munster & Italy)
Salesi Ma'afu (Brumbies)
Mark Regan (Bristol Rugby, England & British Isles)
Schalk Brits (Stormers)
Brent Cockbain (Wales & British Isles)
Justin Harrison (Ulster Rugby & Australia)
Luke Charteris (Newport Gwent Dragons & Wales)
Troy Flavell (Blues & New Zealand)
Jerry Collins (Hurricanes & New Zealand)
Martyn Williams (Cardiff Blues, Wales & British Isles)
Rocky Elsom (Waratahs & Australia)