May 18 (Reuters) - Workers at Puig's PUIGb.MC Vacarisses cosmetics factory near Barcelona will hold a 24-hour strike on May 20 over pay disparities between employee groups, trade union CGT said on Monday.

Puig is in talks with U.S. cosmetics group Estee Lauder EL.N over a potential merger that could create one of the world's largest beauty companies.

• CGT said the dispute relates to differences in economic compensation between groups within the same company and accused Puig of failing to address the issue.

• Puig did not immediately reply to a request for comment.

• The strike will affect all three shifts at the factory, CGT said.

• The union also plans to stage protests outside Puig's corporate headquarters in L'Hospitalet de Llobregat, near Barcelona.

• Workers could consider further measures if the company does not present sufficient proposals, CGT added.

• The Vacarisses plant produces cosmetics and skincare products for brands including Isdin, Charlotte Tilbury, Byredo, Loto del Sur, Dries Van Noten, L'Artisan and Uriage.