The argument over prize money and the dispute over restrictions on jockeys using mobile phones have led to alleged threats to connections.

The Jockey Club, which regulates racing in Britain, says it will take the reports seriously.

"It is unacceptable for pressure to be applied to give up opportunities to earn a living," said a statement.

Senior Steward Julian Richmond-Watson added: "We are very concerned about the reports we have received from our own officials as well as those reproduced in the press about pressure being placed on individuals in relation to the recent disputes."

Trainer Norma Maccauley told Wednesday's Racing Post newspaper that one of her owners had received a phone call suggesting his horse should not run.

Richmond-Watson said: "As the regulatory authority, we are not prepared to turn a blind eye to such reports.

Whether there is any substance to the rumours or not, the talk of such incidents is damaging in itself Jockey Club official Julian Richmond-Watson

"Consequently, we have taken the view that due to their gravity and nature, the rumours we are hearing and allegations that are being made warrant further investigation by our security department.

"Whether there is any substance to the rumours or not, the talk of such incidents is damaging in itself and one would hope that such rumours were misplaced, but if they are found to be true then appropriate action will be taken."

At Wolverhampton last Saturday some owners, trainers and jockeys staged a boycott over cuts in prize money.

The reductions have been imposed because bookmakers' profits, which help fund the sport, have dipped.

The dispute over jockeys' use of mobile phones caused a Sandown Park meeting to be called off earlier this month after the majority of jockeys refused to ride in protest.

The Jockey Club introduced a ban on riders using phones in the weighing room as part of an effort to boost racing's integrity.

It followed a court case in which a former jockey admitted using his phone to pass on inside information to punters.

But jockeys are furious they cannot use phones at racecourses, saying they need to keep in touch with agents and trainers over forthcoming rides.