SAN FRANCISCO, July 24 (Xinhua) -- The world's largest social media network Facebook has signed a new agreement with the U.S. west state of Washington to ban discriminatory advertisements on its platform, Attorney General (AG) of Washington state Bob Ferguson said Tuesday.

Under the legally binding agreement, Facebook will make significant changes to its advertising platform, so as to end the practice of allowing advertisers to exclude certain groups based on race, religious belief and sex orientation from viewing advertisements of housing, credit, employment, insurance and public accommodations.

Ferguson said these changes will be completed within 90 days and go effective nationwide, though the agreement is legally binding in Washington.

"Facebook's advertising platform allowed unlawful discrimination on the basis of race, sexual orientation, disability and religion," said Ferguson. "That's wrong, illegal, and unfair."

The new agreement was a result of a 20-month probe by Ferguson's office, which found that the advertisers were excluding users by race when they use Facebook's "multicultural affinity" category in its ad targeting tool.

Because of the advertisers' discrimination, African-American, Latinx and other ethnic affinities were prevented from seeing their ads.

Facebook had promised to improve enforcement of its prohibition against discrimination in advertising for housing, employment or credit in February 2017, but the Washington AG Office said the social media giant had failed to implement its commitment.