Mitt Romney
Mitt Romney Reuters

The president of an influential American Christian organisation, Family Leader, said Republican candidate Mitt Romney "cannot be trusted on the core issue" and accused the former governor of Massachusetts to a politician who plays "smokes and mirrors".

Bob Vander Plaats told International Business Times UK: "If I was hiring somebody for a job, my first question would be can I trust the guy? Not only has he been on both sides of a multitude of issues, he has been passionately on both sides of issues."

Plaats, who endorsed rival candidate Rick Santorum before he won the Iowa caucus on 3 January, said: "He says one thing and then does another.

"In our faith we say one woman, one marriage. He presided over gay rights in the state of Massachusetts. In healthcare, he said he would repeal Obamacare but if anyone believed that they need to take a serious dosage of reality. The list goes on and on."

Plaats was also critical of how Romney, who admitted paying less than 15 percent tax on his multimillion-dollar income, handled questions anout his tax returns. "The subtext is there is something in those tax returns that he doesn't want the public to see," said Plaats.

"But again he's playing games with the question. When he answered the question in the South Carolina debate he was just waffling. It's not as if he didn't know it was coming."

The three other remaining candidates - former speaker Newt Gingrich, Rick Santorum and Ron Paul - now head to the all-important Florida primary on 31 January, the largest state and the biggest test so far for the candidates.