Walker was to have ridden Scapolo in tomorrow's $200,000 Makfi Challenge at Hastings, but has been stood down.
He did not answer calls last night.
RIU general manager Mike Godber said that in view of the seriousness of the charges, the unit had recommended to New Zealand Thoroughbred Racing that Walker's licence be suspended pending a hearing.
"The allegations before Mr Walker are serious and threaten the very fabric of thoroughbred racing.
"We therefore consider the continued participation of Mr Walker in racing prior to the JCA [Judicial Control Authority] hearing would pose an unacceptable risk to the image, interests and integrity of racing."
The charge is identical to the one Australian great Damien Oliver faced in November 2012, when he was disqualified for 10 months for pleading guilty to placing $10,000 on another runner, which won, in a race in which he rode the beaten favourite. Oliver came off disqualification late last year to win the Melbourne Cup on Fiorente.
Walker failed to profit from his alleged efforts - Watch Your Man finished eighth, 6.3 lengths from the winner, Stella Bella, and the best St Ransom could do was fourth, 3.6 lengths from the winner.