Guests at Christina Aguilera's wedding had to sign a three page secrecy agreement.

The singer insisted all 150 guests agree not to reveal details of her special day. Some of the specifics she wanted kept quiet were the cake, rings, speeches, and most importantly her dress.

"You have to sign your life away," one guest told the Mail On Sunday. "It's three pages long."

The bizarre demand came after one guest tried to sell their invitation to the event – an ornate document encased in a box full of flowers. This is explained at the start of the document.

"It starts, 'It came as a great shock to us that one of our guests has been trying to sell their invitations.'" said the Mail's source. "We are sorry to have to ask you, our dear friends and honoured guests, to sign this agreement but we feel it is the only way to ensure the security of our wedding."

Aguilera married music business man Jordan Bratman yesterday in California