By Jana Winter

 FoxNews.com

An Arizona sheriff says U.S. Border Patrol officials have repeatedly told him they have been ordered to reduce -- at times even stop -- arrests of illegal immigrants caught trying to cross the U.S. border.

Cochise County Sheriff Larry Dever told FoxNews.com that a supervisor with the U.S. Border Patrol told him as recently as this month that the federal agency’s office on Arizona's southern border was under orders to keep apprehension numbers down during specific reporting time periods.

“The senior supervisor agent is telling me about how their mission is now to scare people back,” Dever said in an interview with FoxNews.com. “He said, ‘I had to go back to my guys and tell them not to catch anybody, that their job is to chase people away. … They were not to catch anyone, arrest anyone. Their job was to set up posture, to intimidate people, to get them to go back.”

Dever said his recent conversation with the Border Patrol supervisor was the latest in a series of communications on the subject that he has had with various federal agents over the last two years. Dever said he plans to relay the substance of these conversations when he testifies under oath next month before the Senate Committee on Homeland Security and Governmental Affairs.

“I will raise my hand to tell the truth and swear to God, and nothing is more serious or important than that,” he said. “I’m going to tell them that, here’s what I hear an

Dever’s charges were vigorously denied by a commander with the U.S. Customs and Border Protection.

“The claim that Border Patrol supervisors have been instructed to underreport or manipulate our statistics is unequivocally false,” Jeffery Self, commander of the U.S. Customs and Border Protection Joint Field Command in Arizona, said in a written statement.

“I took an oath that I take very seriously, and I find it insulting that anyone, especially a fellow law enforcement officer, would imply that we would put the protection of the American public and security of our nation’s borders in danger just for a numbers game," he said. "Our mission does not waiver based on political climate, and it never will. To suggest that we are ambiguous in enforcing our laws belittles the work of more than 6,000 CBP employees in Arizona who dedicate their lives to protect our borders every day.”

In recent days, Homeland Security Secretary Janet Napolitano has said the U.S.-Mexican border is more secure than ever, and Homeland Security officials have used recent statistics to support those claims.

"There is a perception that the border is worse now than it ever has been," Napolitano said at the El Paso border crossing last week. "That is wrong. The border is better now than it ever has been."

Dever doesn’t agree.

“Janet Napolitano says the border is more secure than it’s ever been. I’ve been here for 60 years, and I’m telling you that’s not true,” he said.

The sheriff of Santa Cruz County, which borders Dever’s Cochise County to the west, said, “This is news to me,” when asked about reports that border agents were being told to turn illegal immigrants back to Mexico rather than arrest them.

“It comes as a complete surprise that that would be something that’s going around,” Santa Cruz County Sheriff Tony Estrada said. “I meet with Dever all the time and I have great respect for him, so I expect he’d come forward and say what he knows and give the source.

“Not knowing who the source is, how reliable that source is, I really don’t have much of a position,” Estrada said. “I’ve been around a real long time and haven’t heard anything like this. By the same token, you learn new things every day.”

Both sheriffs are elected officials. Dever is a Republican, Estrada, a Democrat.

Others have questioned the methodology and conclusions of the Homeland Security numbers showing the border is more secure.

Mark Hanna, CEO of Real Life Enterprises, a Phoenix-based technology integration and security company, has testified before the Arizona Senate about what he called Homeland Security’s flawed methodology used to compile border security statistics. Hanna maintains the numbers are dangerously misleading.

Hanna, who is currently working on a private/public partnership pilot program along the Arizona border, said he attended a February conference at which Michael Fisher, chief of the United States Border Patrol, and Mark S. Borkowski, assistant commissioner for technology and innovation acquisition, U.S. Customs and Border Protection, showed off charts indicating arrests were decreasing and argued the border was more secure. The charts also showed an increase in marijuana seizures along the border and an increase in Border Patrol agents.

But those charts left out crucial data, Hanna said.

“Since we don't know how many illegal crossings are occurring, then a decrease in apprehensions might mean that there are fewer illegal crossings, and the border is more secure. But it could also just as easily mean that more illegal border crossings are occurring, and we're just not catching as many. In order to know how secure the border is, you need to know how many are crossing and the threat level of those who are crossing illegally," he said.

“It is a very dangerous condition for the secretary of Homeland Security to be using incomplete data to form such a conclusion, and then repeatedly announce these conclusions as fact,” he said.

The Department of Homeland Security did not return repeated requests for comment on Hanna’s specific challenges to the agency’s methodology.

Whatever the methodology, Dever said the numbers don’t accurately describe what’s happening on the ground.

“We do not know who’s crossing that border, but that anyone who wants to can. That’s the message our nation needs to hear, that anyone who wants to can, and is. And our own Department of Homeland Security does not have clear definition of what securing the border even means," Dever said.

“People are disgusted, the smiles are gone off their face, their general sense of welfare been taken away from them and until that’s returned you can throw all the numbers on the board. … I’ll tell Napolitano, in spite of all of your declarations and efforts to the contrary, things are not safe. No, they are not secure.

“You can use your numbers to say it’s more secure, but it does not define a sense of safety or well-being. You can say it’s more secure, but it’s more dangerous than ever.”