An online petition started by a Walmart employee urging the retail giant to reform and investigate misconduct over a bribery scandal at a Mexican subsidiary had gathered some 4,700 signatures late Friday.

The employee, who identified herself as Venanzi Luna, a department manager who has been working at the company for seven years, said the scandal prompted her to collect the signatures demanding change at the top of the firm, including company chiefs.

"I've given a lot to this company and I'm very angry that top executives at Walmart are said to be involved in bribing public officials in Mexico and then trying to cover the whole thing up," she wrote in the online petition posted at protest site

"I'm worried because while I am working hard, now I'm hearing that they're risking our company by lying and cheating," Luna wrote.

In the petition letter, she urged supporters to sign calling for the resignation of top Walmart executives and a thorough investigation into bribery allegations.

The New York Times reported last week that the retail giant's largest non-US subsidiary made illicit payments worth some $24 million to win market dominance and tried to cover them up.

"When we consider how a failure of this magnitude occurred, we cannot help but conclude that the board did not exercise necessary leadership and independence," Luna wrote in the petition.