Mitt Romney's Republican rivals came out strong Friday to denounce phone calls made in early-voting states that pretend to be polls but raise critical questions about Romney's Mormon faith, as the New Hampshire attorney general set out to investigate the matter.

Western Wats, a Utah-based company, placed the calls that initially sound like a poll but then pose questions that cast Romney in a harsh light, according to people who received the calls. In politics, this type of phone surveying is called "push polling" — contacting potential voters and asking questions intended to plant a message, usually negative, rather than gauging attitudes.

The 20-minute calls started on Sunday in New Hampshire and Iowa, and posed questions about Romney's Mormon faith and his military deferments. Sources in the Romney campaign say the calls have also spread to South Carolina, though they appear to be coming from a different company.

The calls made favorable statements about Republican rival John McCain, but McCain said they're not his doing and he wants them stopped.

"It is disgraceful, it is outrageous, and it is a violation, we believe, of New Hampshire law, as well as any kind of decency or good taste," he said.

His campaign asked the attorney general to investigate, and McCain, campaigning Friday in Colorado, asked other candidates to join in the request.

One McCain adviser, Chuck Douglas, said "we believe it is being done by one of the other campaigns. We don't know which one."

Romney said Friday that "I think the attempts to attack me on the basis of my faith are un-American."

Later asked about donations to his campaign that had apparently come from employees of Western Wats, Romney said he was not familiar with the company.

"It's not very likely that people who support my campaign are going to launch calls attacking (me) on the basis of my faith, so I think that is kind of remote," he said.

Other candidates responded with equal disgust, and denied responsibility.

"There is no room for this sort of thing in politics. Our campaign does not support or engage in these types of tactics and it is our hope other campaigns will adhere to the same policy," Katie Levinson, spokeswoman for candidate Rudy Giuliani, said in a statement.

"There is no room for this kind of smut in a Republican primary election," candidate Fred Thompson's spokesman Todd Harris said. "This kind of robo-dial bigotry which tears down Republicans today will only serve to prop up Democrats tomorrow. It has to end and end now."

New Hampshire's Deputy Attorney General Bud Fitch said the state has never prosecuted a case involving such calls but was moving forward. He cautioned against expecting an immediate resolution.

"Generally, these investigations can take at least several days and sometimes several weeks," Fitch said.

At least seven people in the two early voting states received the calls, some as recently as Thursday. Among the questions the caller asked was whether the person receiving the call knew Romney was a Mormon, that he received military deferments when he served as a Mormon missionary in France, that his five sons did not serve in the military, that Romney's faith did not accept blacks as bishops into the 1970s and that Mormons believe the Book of Mormon is superior to the Bible.

A spokesman for Western Wats would not comment on whether it made the calls. "Western Wats has never, currently does not, nor will it ever engage in push polling," its client services director, Robert Maccabee, said in a statement released Thursday night.

"It started out like all the other calls. ... Then all of the sudden it got very unsettling and very negative," said Anne Baker, an independent voter from Hollis, N.H., who received one of the calls.

In Iowa, Romney supporter and state representative Ralph Watts got a call on Wednesday.

"I was offended by the line of questioning," Watts said. "I don't think it has any place in politics."

Romney's Mormon faith has been an issue in his presidential bid, especially with conservative evangelicals who are central to his strategy to cast himself as the candidate for the GOP's family values voters.

Baker, who got a call in New Hampshire, said the caller initially wouldn't tell her who was behind it. Eventually, Baker was told the caller was from Western Wats.

Last year, Western Wats conducted polling that was intended to spread negative messages about Democratic candidates in a House race in New York and a Senate race in Florida, according to reports in The Tampa Tribune and the Albany Times Union, which also said Western Wats conducted the calls on behalf of the Tarrance Group.

That Virginia-based firm now works for Romney's rival, Rudy Giuliani. The campaign has paid the firm more than $400,000, according to federal campaign reports.

In his statement on behalf of Western Wats, Maccabee said the company was not currently conducting "any work for ... The Tarrance Group in the state of New Hampshire or Iowa, nor have we for the period in question."

Maccabee added that confidentiality agreements prohibit the company from commenting on specific projects or clients.

Ed Goeas, chief of the Tarrance Group, said there is no connection between the Giuliani campaign and Western Wats.

"I know absolutely it's not us," Goeas said. "I can say with absolute, no, it's not us."

Western Wats also worked for Bob Dole's presidential campaign in 1996. Employees said they used such calls at that time to describe GOP rival Steve Forbes as pro-abortion rights.

New Hampshire law requires that all political advertising, including phone calls, identify the candidate being supported. No candidate was identified in the calls.

FOX News' Mosheh Oinounou, Carl Cameron and Shushannah Walshe and The Associated Press contributed to this report.