MEXICO CITY — Mexico’s federal government should investigate allegations of a vast bribery campaign by top executives of Walmart’s Mexican subsidiary to build stores across the country, the head of a watchdog group said Sunday.

Eduardo Bohorquez, director of Transparencia Mexicana, said international conventions obligate Mexico’s government to get involved even though only local officials have been linked to the scandal.

“The laws in Mexico and the United States relating to bribery are in effect, so the practices (of legal business) should be the same in both countries,” he said.

Government officials declined Sunday to comment on the allegations contained in a New York Times report that said Walmart Stores Inc. failed to notify law enforcement after its own investigators found evidence that millions of dollars in bribes had been paid in Mexico to spur the company’s rapid expansion there.

A lawyer for Walmart de Mexico, Juan Manuel Torres Landa, said the company had no comment on any of the allegations.

One of every five Walmart stores now is in Mexico, and it is Mexico’s largest private employer, with 209,000 employees.