More than 12 million Americans think that giant lizards dressed in suits are running the United States.

The conspiracy theory, which suggests that President Barack Obama is some kind of real-life lizard king, is believed by around 12.5m people (4 percent of the population), according to a report by Public Policy Polling.

But the lizard theory was by no means the only sinister idea with traction among the people who make up the world's most powerful nation.

As well as being a lizard, Obama is also the devil, according to millions of Americans. Figures extrapolated from the poll results reveal that more than 40 million people hold this view, perhaps encouraged by a recent History Channel programme which cast an actor bearing a striking physical similarity to Obama as Satan.

Obama Satan
Satan, as portrayed by the History Channel.

More than one in 10 Americans think their own government gave the green light to the 9/11 terror attacks on the World Trade Centre in New York. Almost three times as many people (28 percent) think former Iraqi dictator Saddam Hussein masterminded the attack.

The most popular theory of all was the classic conspiracy theory surrounding the assassination of President Kennedy in 1963. That alleged that the killing was the work of shadowy forces, rather than Lee Harvey Oswald. About one in two people polled subscribe to arguably the world's most famous conspiracy of all time.

Second most popular was the claim that former president George W Bush lied about weapons of mass destruction (WMD) in the build-up to the invasion of Iraq in 2003. Of those polled, 44 percent believed this, representing 138,122,178 people out of the total population of the US.

Next in line was global warming, with 37 percent saying that climate change was a fraud made up by scientists. Fourteen percent think Bigfoot is real. The same number believe crack cocaine was invented by the CIA as a mind control device.

And former Beatle Paul McCartney is believed to be have been dead for 47 years by 5 percent of the population.

Many people believe that the preponderance of conspiracy theories is indicative of the online culture, in which the internet propagates outlandish ideas that gain credibility.

Yet, according to 5 percent of Americans, the government has already taken steps to curb such potentially seditious activity by spraying the public with mind control gases through aeroplane contrails. After Mitt Romney's query last year as to why plane windows do not open, it appears Americans' suspicions about air travel knows no bounds.

The full list and the number of believers:

JFK was killed by conspiracy51 percent160,096,160
Bush intentionally misled on Iraq WMDs44 percent138,122,178
Global warming is a hoax37 percent116,148,195
Aliens exist29 percent91,035,072
New World Order28 percent87,895,931
Hussein was involved in 9/1128 percent87,895,931
A UFO crashed at Roswell21 percent65,921,948
Vaccines are linked to autism20 percent62,782,808
The government controls minds with TV15 percent47,087,106
Medical industry invents diseases15 percent47,087,106
CIA developed crack14 percent43,947,966
Bigfoot exists14 percent43,947,966
Obama is the Antichrist13 percent40,808,825
The government allowed 9/1111 percent34,530,544
Fluoride is dangerous9 percent28,252,264
The moon landing was faked7 percent21,973,983
Bin Laden is alive6 percent18,834,842
Airplane contrails are sinister chemicals5 percent15,695,702
McCartney died in 19665 percent15,695,702
Lizard people control politics4 percent12,556,562