The White House has officially declared planet Earth to be an alien-free zone - but then they would say that, wouldn't they?

The denial by the American government that it has ever covered-up evidence that aliens are living among us was made by Obama administration official Phil Larson on the White House website.

He was responding to two public online petitions signed by thousands of Americans calling for the existence of aliens to be publicly acknowledged.

"Thank you for signing the petition asking the Obama Administration to acknowledge an extraterrestrial presence here on Earth," he wrote.

"The U.S. government has no evidence that any life exists outside our planet, or that an extraterrestrial presence has contacted or engaged any member of the human race."

He added: "In addition, there is no credible information to suggest that any evidence is being hidden from the public's eye."

Larson comments were made on the White House's 'We The People' site which encourages public participation in the political debate, much like the e-petitions website in the United Kingdom.

"The fact is we have no credible evidence of extraterrestrial presence here on Earth," he concludes.

One petition demanded that President Obama disclose to the American people the "long withheld knowledge of government interactions with extraterrestrial beings" and called for open Congressional hearings to "allow the people to become aware of this subject through those whose voices have been silenced by unconstitutional secrecy oaths".

While the over 12,000 signatories to another petition said they "strongly urge the President of the United States to formally acknowledge an extraterrestrial presence engaging the human race and immediately release into the public domain all files from all agencies and military services relevant to this phenomenon."

"The people have a right to know," the petition adds. "The people can handle the truth."

Of course Larson's response is unlikely to satisfy those who believe governments have been covering up alien contact for years.

The truth is out there, somewhere.