ZHENGZHOU, China — Staff at a supermarket in central China refused to use a local dialect when issuing appeals to find a missing grandmother — insisting on the use of Mandarin even though the woman could not understand it, a local newspaper has reported.

A woman with the surname Ni had taken her children and 60-year-old mother shopping at a three-storey store in Zhengzhou, the capital of Henan province, on Sunday (May 13).

She became separated from them when she went to eat at the canteen while her mother took the children off to play.

But when Ms Ni asked the supermarket help desk to make an announcement in her mother's local Henan dialect, they refused, local paper Dahe News reported earlier this week.

Staff said they would only broadcast in Mandarin, which her mother, who is from a rural village, cannot understand.

The Chinese government has long promoted the use of Mandarin — known as Putonghua or common speech — as the official language.

There are still thousands of different dialects spoken around the country.

While the National Common Language Law promotes the use of Mandarin in daily life, and states that public services should use it, the use of these local dialects is not forbidden.

The customer service centre at the store said it was required to make all announcements in Mandarin as it was the language of the country and represented its overall image.

"You can make a request for customer service to broadcast in a dialect, but I don't think it would be accepted," a worker told the paper.

"Because if we do this, it could affect other customers" who may not know what was being said.

Ms Ni pointed out that many elderly people in Zhengzhou are from rural areas and do not speak Mandarin.

She said the policy meant that she had spent an hour searching three floors of the supermarket to look for her mother and children.

She added that her mother had not lived in the city for long and did not have a mobile phone. However, she was eventually able to track them down on the first floor.

The Chinese government drive to promote Mandarin in areas like education and media has come at the expense of local dialects and critics have warned it is eroding China's diverse regional cultures.

In 2014 the news channel of Guangdong TV in the south of the country caused outrage when switched all content and anchors from Cantonese, which is spoken by more than 70 million people, to Mandarin. The two forms of speech are mutually unintelligible.

A 2012 study in Shanghai found that only 60 per cent of pupils surveyed, who are taught in Mandarin, could speak the Shanghainese dialect. SOUTH CHINA MORNING POST