Retail giant Gap Inc has been accepted into membership of United Kingdom-based labour rights watchdog the Ethical Trading Initiative (ETI).

The San Francisco-based company, which earlier this month announced plans to help set up a unionised factor in El Salvador, is the third US corporation to join the alliance.

"Joining ETI is an important step in our ongoing efforts to evolve our program and find sustainable approaches that will improve garment factory working conditions around the world," Gap chief administrative and compliance officer Anne Gust said.

"We look forward to learning from ETI members and working collaboratively to address global labour issues that affect workers in garment manufacturing and other sectors."

ETI, which promotes good practice in supply chain labour conditions for workers producing goods for the UK market, accepted Gap for membership after a successful assessment of its commitment to meeting international labour standards with its suppliers.

Gap, which does business with about 3000 garment factories in about 50 countries, requires all suppliers to comply with its Code of Vendor Conduct defining labour and health and safety standards.

In addition, the company employs about 90 full-time staff worldwide to monitor supplier factories for compliance issues and work with industry bodies to improve conditions.

ETI is made up of 37 companies and 16 non-governmental organisations and trade unions.