An official statement said Prince Salman bin Hamad Al Khalifa wrote to Prince Charles to send his regrets after questions emerged over inviting a member of Bahrain's Sunni monarchy, which has waged a wide-ranging crackdown against Shiite protesters calling for more freedoms.
Bahrain's rulers have imposed martial law and are backed by a Saudi-led military force to try to quell the uprising. At least 30 people have died in Bahrain since mid-February, including four who died while in official custody, and many well-known activists and lawyers have been imprisoned.
The prince was among more than 40 foreign royals invited to the wedding at London's Westminster Abbey on April 29. Rights campaigners complained Saturday when palace officials said he was invited, and some petitioned Foreign Secretary William Hague to revoke the invitation.
The prince said he was "saddened and troubled" by British reports about his attendance.
"While these (media reports) have certainly highlighted a number of significant issues currently facing the Kingdom of Bahrain, they have fundamentally misrepresented my own views, outlook and position on recent events and thus, clearly sought to involve my potential attendance as a political proxy for wider matters involving Bahrain."
A Buckingham Palace spokesman confirmed that he was informed Sunday about the prince's decision.
The prince said Bahrain has the highest respect for Britain's royal family, and that he wished William and Middleton "all good wishes for Friday and every possible happiness for the future ahead."