The ex-wife of Amazon founder and chief executive Jeff Bezos has pledged half her fortune to charity, following in the footsteps of billionaires Warren Buffett and Bill Gates.

MacKenzie Bezos finalised her divorce in April and reportedly got a stake in the online shopping giant worth more than 35 billion dollars (£27.5 billion).

It was earlier reported Ms Bezos would get 4% of Amazon, thought to be worth around $35.6 billion (£27 billion), through the annulment.

The Giving Pledge was started in 2010 by 40 of the wealthiest people in the US.

It involves billionaires pledging more than half of their wealth to charitable causes either while they are alive or in their wills.

Bill and Melinda Gates, who have stakes in Microsoft, and Facebook boss Mark Zuckerberg are among the well-known names who have contributed to the fund.

Ms Bezos said in a letter: "We each come by the gifts we have to offer by an infinite series of influences and lucky breaks we can never fully understand."

"In addition to whatever assets life has nurtured in me, I have a disproportionate amount of money to share."