New concerns are being raised about the potential use of performance-enhancing drugs in schoolboy rugby.

Drug Free Sport New Zealand is worried New Zealand could follow the lead of South Africa and England.

A dozen young South African players and a similar number of English boys have tested positive for illegal drugs.

Drug Free Sport chief Graeme Steel says the preconditions for doping are already in place here.

He says rugby is increasingly a high-pressure high-rewards environment, and supplements are widely available.