The controversy surrounding The Wine Advocate and Spanish wine expert Pancho Campo continues to rumble on.

Campo is a member of the Institute of Masters of Wine and the group has responded to allegations surfacing in the media by instigating a formal investigation.

As head of the Wine Academy of Spain, Campo has organised numerous tastings around the world, some of which have featured Jay Miller, the Spanish correspondent for Robert Parker's The Wine Advocate.

Decanter writer Jim Budd is one of a number of wine bloggers who have made allegations against Campo, suggesting his company has been charging Spanish wineries for access to Miller and, by extension, features in the renowned wine magazine.

Both Campo and Miller have strongly refuted the claims, but the Institute of Masters of Wine said it has "become aware" of the allegations and has begun its own investigation.

A statement from the group said: "No conclusions have been reached, investigations will continue, and no further statement will be made until such time as the investigation has concluded."

The group stated that such investigations are undertaken very infrequently, with a "mere handful" taking place in the lifetime of the institute.

Its statement continued: "[The institute] takes alleged breaches of its Code of Conduct very seriously, and investigates all such alleged breaches once a formal complaint is made.

"In the event that a breach of the code is proven, a range of sanctions is available to it."

Robert Parker has begun his own investigation into the allegations, yet Miller has now resigned from his post at the magazine.

Miller insists that the allegations had no bearing on his decision to quit, claiming it is simply the right time to go it alone.