Civil rights body accuses Customs and Border Protection agents of using excessive force against US citizens and immigrants

US citizens and immigrants with full legal rights to reside in America are being subjected to widespread physical and legal abuses at the hands of US border guards at crossing points with Mexico, according to the American Civil Liberties Union.

The ACLU has sent a formal letter of complaint to the department of homeland security to protest what it says is a sharp increase in human rights violations by US government agents along the Mexican border.

The civil rights body accuses Customs and Border Protection agents of wielding excessive force, carrying out unwarranted strip searches, detaining people for long periods without explanation and coercing individuals into surrendering their legal rights and citizenship documents.

"We are seeing widespread federal abuses against US citizens and non-US citizens alike. Something is going very wrong here, and it needs looking into," said Sean Riordan, an ACLU lawyer and signatory to the complaint.

The ACLU is requesting an investigation into the instances of alleged excesses at the Mexican border. It cites 11 cases of individuals who claim they were mistreated at various border crossings.

Among them are Hernan Cuevas who crossed from Mexico to the US at Calexico/Mexicali on 19 May 2011. A Chilean businessman who works for an industrial manufacturing corporation, he spends most of his working life travelling to and from America and had never before had any trouble with border agents.

He was stopped and his car searched, and when he tried to complain that his property was being roughly handled was astonished by the reaction. He was handcuffed and chained by his big toe to a metal bench, and refused the right to call a lawyer or the Chilean embassy.

In sweltering heat, he asked repeatedly for water but was also refused. Before he was released after almost four hours of detention, an agent allegedly said to him: "I don't give a fuck of your educated manners and all your corporate bullshit. This is my country now and when you are here, you listen to me. I don't like your kind that takes our jobs and uses our system."

Cuevas told the Guardian that he was utterly taken aback by what had happened. "I never would have believed that such behaviour was possible in a civilised country, let alone the US," he said.

"I thought this kind of thing only happened in films about banana republics. These guys behaved as though they were above the law."

ACLU contends that Cuevas's experiences were part of a pattern of abuse by Customs and Border Protection that must now be investigated and rectified. CBP is America's largest law enforcement agency and has expanded dramatically in recent years. The numbers of its border patrol guards has grown from 5,000 in the mid 1990s to more than 20,000 today, and has doubled in just the past six years.

Riordan said that the exponential expansion of the agency had not been accompanied by a proporational growth in training, oversight and accountability, creating a vacuum out of which the current problem of abuses had been allowed to fester.

A spokesman for CBP said that ACLU's letter of complaint had not yet been received and made no comment at this stage.

The other cases highlighted by ACLU include Edith Collins-George, a US citizen who was detained without explanation in March 2010 at the Calexico/Mexicali crossing having visited her mother in Mexico.

She says she was told by officers: "You don't have rights here", and was then pushed up against a wall and searched, with officers touching her breasts and genitals.

Another of the cited cases, Trinidad Muraira de Castro, was crossing at Brownsville, Texas on a temporary visa with her two daughters who were born in the US and are thus US citizens.

The whole family was detained and interrogated for about 10 hours, at which point De Castro says she broke down and made a false confession that her daughters were not born in America and had no right to be there.

On that basis the family was turned back at the border and her visa confiscated.

Last month the justice department announced that it had decided not to prosecute a US patrol agent who shot and killed a Mexican teenager in June 2010 near the El Paso border crossing. Sergio Hernandez-Guereca, 15, was shot by the unidentified CBP officer after reportedly throwing rocks at the border line.