MEXICO CITY, May 12 — Mexico’s labour ministry yesterday said it found "serious irregularities” in a union-led vote at the General Motors Co plant in the city of Silao, and ordered the automaker’s union to re-hold a vote within 30 days.

The Mexican ministry’s move followed pressure earlier in the day by US lawmakers on GM to ensure worker rights at the Silao plant, adding to concerns from global labour advocacy groups.

Mexican officials had previously said that some ballots were destroyed during the vote in April, which was intended for workers to ratify their collective contract.

The ratification is required under a Mexican labour reform to ensure workers are not bound to so-called protection contracts, which are signed behind workers’ backs and prioritise company interests.

Such votes are part of the broader effort underpinning promises in the United States-Mexico-Canada Agreement (USMCA) free trade pact to uphold worker rights.

The ministry said in yesterday’s statement that the GM vote had "violated principles of safety and certainty that should govern every democratic process.”

GM has denied wrongdoing and said it condemned labour rights violations. — Reuters