LONDON, June 8 (Reuters) - Big tech firms must introduce safety measures on children's phones to prevent them from circulating nude images, British Prime Minister Keir Starmer said on Monday.

Under the new plans, companies like Apple and Google should build or activate technical solutions on smartphones and tablets to detect and block nude images for children, the government said. Adults would still be able to take, share or view nude content through an age verification process.

"If companies do not act within three months, the government will bring forward legislation to force them to activate the technology," the government said in a statement accompanying Starmer's announcement.