The lawsuit against China Labor Watch was filed in a Chinese court this week by HEG Electronics, which produces mobile phone components for Samsung and China's Lenovo Group, Samsung said Thursday.
China Labor Watch rejected the lawsuit as a "public relations action."
In its August report, China Labor Watch had accused the company in Guangdong province in southern China of hiring more than 10 child workers under the age of 16.
Samsung said a joint investigation with HEG and another probe by local authorities found no child labour. HEG and Samsung called on China Labor Watch to apologize and to admit its allegation as false. It said the group has not responded to its request.
Since 2012, China Labor Watch has researched working conditions at Samsung's suppliers in China. It uncovered some cases of child labour, which prompted Samsung to adopt a pledge not to permit any use of under-age workers.
The South Korean company began reporting annually to its investors the state of labour conditions at its Chinese suppliers.
But this is the first time that a legal action was taken against by a Samsung supplier in response to an allegation of child labour.
"CLW has endangered the very existence of HEG by undermining the confidence of its business partners and employees," HEG said in a statement.
China Labor Watch said its report demonstrated a list of child workers' identities. It also said the Chinese court has no jurisdiction over the group.
"This lawsuit is a public relations action," said Li Qiang, executive director at CLW, in a statement. "If they were serious, HEG and Samsung would file the lawsuit in America."
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