Chinese environmental groups on Thursday singled out Apple for failing to tackle concerns over pollution and the health of workers at plants making parts for trendy gadgets such as its iPhone.

In a new report, the groups said the US giant ranked last in a survey of how 29 multinational technology companies respond to inquiries about pollution and workplace health hazards at factories in their supply chain in China.

The study reflects over a year's work by more than 30 Chinese environmental NGOs to pressure multinational companies into being more accountable for their impact on the country's environment.

"Apple has broken its promise on three aspects of supply-chain social responsibilities," said the report, the main author of which is the Institute of Public and Environmental Affairs, an independent Beijing-based organisation.

"On Apple's supply chain, some workers were poisoned and disabled, neighbourhoods and communities were polluted while there were severe infringement of workers' rights, interest and dignity," the report said.

It commends Hewlett-Packard, British telecoms operator BT, Alcatel-Lucent, Vodafone, Samsung, Toshiba, Sharp and Hitachi for taking some steps to change poor practices or step up supervision of manufacturing.

Apple was not the only company the report cited as failing to act or respond to concerns -- Nokia, LG, SingTel, Sony and Ericsson also fared poorly in the survey.

But the US company was the worst, the groups said, for "dodging" questions from the public and requests from environmental groups for investigations.

"You should educate yourself. We do more than any other company on the planet," the report quoted Apple chief executive Steve Jobs as writing in response to an Internet user's question about its social responsibility record.

Apple's website says it is committed to ensuring the highest standards of responsibility and insists suppliers provide safe working conditions, treat workers with dignity and be environmentally responsible.

A Hong Kong-based spokeswoman with Apple on Thursday denied the claims made in the report.

"Apple has a vigorous auditing programme that investigates suppliers and other parts of the business chain. We audit throughout... We actually have had an extensive auditing programme since 2006," she told AFP.

China's emphasis on economic growth over the past three decades has led to notoriously lax workplace safety as well as widespread industrial pollution.

One incident the groups cited Apple for failing to address was the poisoning of 49 workers at Lianjian Technology, owned by Taiwan-based Wintek, which reportedly makes touchscreens for Apple.

The case was widely publicised in Chinese media last year when the workers were hospitalised after being exposed to the chemical cleaning agent n-hexane. Workers claimed Apple did not respond to their complaints, the report said.

"Some workers recalled that representatives from Apple had visited the factory, but they never told them n-hexane, which was used to increase the output and rate of qualified products for Apple, was toxic and harmful".

In response to enquiries about the incident by various labour rights groups, Apple only insisted it "will never disclose any information about suppliers," according to the report.

Apple's highest-profile supplier in China is Taiwan-owned high-tech giant Foxconn, whose treatment of its workers was put in the spotlight by a spate of suicides that saw at at least 13 mainland employees take their lives in 2010.