The technology giant said that it was committed to the highest standard of social responsibility.

The comments come after a report by Chinese environmental groups claimed a number of Apple manufacturers were discharging harmful pollutants.

Chinese companies have often been criticised for focusing on output rather than environmental issues.

The report by the Institute of Public and Environmental Affairs (IPE) and other non-governmental environment groups also said that one factory in the city of Taiyuan emitted irritating gases and residents had reported difficulty opening their windows.

In response, Apple told the BBC’s Michael Bristow that the company had a tough code of conduct for all its supply firms and it audited many of them.

But a company report released earlier this year found dozens of suppliers across the world were mishandling dangerous chemicals.

More than 100 workers were contaminated at one Chinese plant.

Environmental groups say China does not have sufficient rules in place to protect the environment and Apple is taking advantage of that.