An “America’s Next Top Model” contestant says producers snatched her crown AFTER she won it fair and square, because they found out … she used to be an escort.

Angelea Preston says things started to go South right before she taped the finale of the All-Star season in 2011. According to a lawsuit she’s filing … Preston told producers, confidentially, prior to filming the season she had been an escort for about a year — and that spread like wildfire to the rest of the cast and crew.

After the finale was taped — and Preston had won the grand prize — she says a casting director called and grilled her about the whole escort business. In the suit, Preston says she admitted it, but insists she was a legal escort and not a prostitute. Despite this, Preston was told she had violated her contract and could not be the winner.