Undercover investigators testing how tough it is to cross the borders into the U.S. had a better than nine-in-10 chance of pulling it off using oral assertions and counterfeit identification, according to a new U.S. Government Accountability Office report.

The report was released the same week as a separate unrelated report that indicates tougher border security isn't deterring illegal entries to the United States.

Tougher security is, however, leading many people to cross through ports of entry — concealed in vehicles or openly using phony documents — according to the report by the Center for Comparative Immigration Studies at the University of California, San Diego.

Even though the smuggling fees are more costly, crossing through ports of entry has more than doubled since 1995 as "the most foolproof way of reducing the physical risk," said Wayne Cornelius, center director.

The center's report was compiled using interviews with more than 3,000 migrants and potential migrants from towns in four Mexican states. It found that fewer than half of the migrants that come to the border are apprehended even once. Nearly all eventually get through.

In the GAO report, a 93 percent success rate was reported by investigators who made 42 crossings on the northern and southern borders from January 2003 to September 2007.

"As a result of these tests, GAO concluded that terrorists could use counterfeit identification to pass through most of the tested ports of entry with little chance of being detected," the report said.

In response to the GAO report the Department of Homeland Security provided written updates on border-protection efforts, including providing updated fraudulent-document training modules, implementing mandatory refresher training and providing advanced equipment to ports of entry with the highest rates of fraudulent-document interceptions.

Cornelius said rather than focusing on border security, a better approach to curb illegal immigration would be to legalize the undocumented, reform the nation's guest-worker visa program and get tough on workplace enforcement.

"Unauthorized migration will decrease only when the majority of potential migrants conclude that the costs and physical risks of clandestine entry are greater than the potential benefits awaiting them on the other side of the border," the report said.

However, Jon Feere of the Center for Immigration Studies contends border security is an important component "to stop more illegal immigration."

Feere also said he believes workplace enforcement is key to promote self-deportation. Unlike Cornelius, Feere says amnesty would only encourage more illegal border crossings.