The Duchess of York has been caught on tape trying to make big bucks off Buckingham Palace... by selling access to her ex-hubby Prince Andrew for more than $700,000.

The prince had no idea these deals were taking place, but a news organization decided to let everyone know... by setting up a sting operation.

There were two secret meetings in New York and London where the Duchess asked for a $40,000 cash advance followed by $700,000 in exchange for providing access to Britain's royal family.

A reporter posed as a wealthy businessman who wanted to strike up some business through the royal family.

Ferguson's spokeswoman confirmed that the recording was authentic. She said the duchess was "devastated" and regretted the embarrassment she had caused.