Anti-tax lobbyist Grover Norquist is lashing out at Republicans who voted to raise taxes, calling them "rat heads in a coke bottle."

Speaking to the Conservative Political Action Conference (CPAC) on Thursday, the Americans for Tax Reform founder employed an unusual metaphor to blast Republicans who violated their pledge to never raise taxes.

"We had the pledge out there and we branded the modern Republican as the party that would not raise your taxes," Norquist explained. "Branding is important. Coca-Cola spends a lot of time, quality control branding Coca-Cola. Everybody knows what's in Coca-Cola. And so you can buy a bottle of Coke, take it home, you don't have to ask what's in it."

"You get two-thirds the way through your bottle of Coke and you look in and there's a rat head in what's left in your Coke bottle," he continued. "You begin to wonder whether you will buy Coke in the future, you go on local TV and you show the cool rat head. Coca-Cola has a very large problem worldwide. It damages the brand."

"Republican elected officials who vote for tax increases are rat heads in the Coke bottle. They damage the brand for everybody else."

Watch this video from CNN, broadcast March 14, 2013.