A Hong Kong judge on Thursday rejected a lawsuit and claims for compensation by the parents of four mainland children, who were among thousands who fell ill two years ago after consuming tainted milk powder.

Hong Kong's Small Claims Tribunal adjudicator Ada Yim ruled that the case should be handled by mainland courts, since the plaintiffs are from the mainland and their children were poisoned there.

The parents had sued the New Zealand dairy cooperative Fonterra in this special administrative region, hoping the courts here would be more sympathetic to their case.

They took this step after lawsuits filed on the mainland were ignored, their lawyer said.

Their children were among 300,000 sickened after consuming milk products deliberately contaminated with the industrial chemical melamine to bluff their way through tests aimed at measuring protein content.

At least six children died as a result of consuming the tainted product.

While Fonterra was never accused of wrongdoing, through a Hong Kong subsidiary it was a minority shareholder in the now-defunct Chinese dairy company Sanlu Group Co, one of the firms at the heart of the milk scandal.

Yim said Fonterra could not be held accountable because, as a minority shareholder, it had no control over the production and distribution of Sanlu milk powder. The New Zealand dairy had three out of seven seats on the Sanlu board - not enough to influence company policy.

"The mainland is undoubtedly the more appropriate forum" for a lawsuit, Yim said.

Peng Jian, who represented the parents, said the judge did not understand the difficulty of navigating mainland courts.

He said he would study the decision before deciding whether to appeal.

Yim's argument that the mainland was a more appropriate jurisdiction "may be well-founded in theory, but it is hard to apply in practice", Peng said.

The four parents, whose children suffered from kidney stones or kidney failure, did not speak to reporters in Hong Kong after the ruling. They were seeking compensation ranging from HK$12,400 (US$1,600) to HK$33,500.

Earlier, in oral arguments, one of the four accused Fonterra of having delayed going public with the faulty Sanlu supplies and profiting from the tactic. However, the New Zealand company was the whistle-blower that alerted the Chinese government to the problem.

Fonterra lawyer David Matthews denied that the company procrastinated and said it lost its NZ$212 million (US$142 million) investment in Sanlu because the company went bankrupt.

Matthews welcomed Thursday's ruling, while acknowledging that Fonterra has "the greatest respect for the claimants".

"This has been a very tragic situation for all of their families," he said.