New Zealand dairy giant Fonterra has denied claims that it approved the use of the industrial chemical melamine in dairy products manufactured by Chinese firm Sanlu. 

Last year, six babies died and around 300,000 more fell ill after drinking Sanlu's baby formula, which was tainted with the industrial chemical melamine.

It is believed that melamine had been used to artificially boost the protein content of milk in order to pass quality checks.

At the time, Fonterra held a 42% stake in the Chinese dairy group.

Fonterra knew of the contamination issue in August, from which time it claims to have pushed for a product recall.

Earlier this month, Sanlu's chairwoman Tian Wenhau was jailed for life over the scandal.

However, since her sentence was handed down she has claimed that a Fonterra-appointed director provided her with a document detailing the EU's permitted levels of melamine.

While Fonterra chief executive Andrew Ferrier confirmed that such a document was provided, he said the company was "vividly clear" to Sanlu that acceptable levels of melamine were "zero".

"Fonterra consistently pushed for a full public recall of contaminated product from 2 August  when we learned of the contamination. Additionally Fonterra clearly communicated both verbally and in writing to Sanlu that its product must contain no melamine," Ferrier said.