Image copyright Twitter Image caption Evan McMullin is a CIA veteran and chief policy director of the House Republican Conference

Former CIA agent Evan McMullin has announced an independent presidential bid as an alternative to Republican nominee Donald Trump.

Mr McMullin, the chief policy director of the House Republican Conference, is backed by an anti-Trump group.

He is likely to face challenges in appearing on some state ballots just three months before Election Day.

The 40-year-old Mormon has never held elected office.

Mr McMullin is an outspoken critic of Mr Trump on social media, calling the businessman an "authoritarian".

"It's never too late to do the right thing, and America deserves much better than either Donald Trump or Hillary Clinton can offer us. I humbly offer myself as a leader who can give millions of disaffected Americans a conservative choice for President," Mr McMullin said in a statement.

Image copyright Twitter

The group Better for America had been reportedly searching for an independent presidential candidate to put up against Mr Trump.

Mr McMullin, who is expected to file his candidacy paperwork on Monday, released a statement to ABC News.

"It's never too late to do the right thing, and America deserves much better than either Donald Trump or Hillary Clinton can offer us. I humbly offer myself as a leader who can give millions of disaffected Americans a conservative choice for President," Mr McMullin said.

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The Utah native graduated from Brigham Young University and has a master's of business administration from The Wharton School at the University of Pennsylvania, according to his LinkedIn page.

He also served as a Mormon missionary in Brazil.

Mr McMullin left the CIA in 2010 after 11 years before working for Goldman Sachs.

He became a senior adviser on national security for the House Committee on Foreign Affairs in 2013 and subsequently the chief policy director of the House Republican Conference.