America's top law enforcement official has declared that immigrants facing deportation have no right to an effective attorney, a move immigration lawyers and the country's top lawyers' guild described as a last-minute evisceration of a constitutional right.

In Wednesday's decision, George Bush's attorney general, Michael Mukasey, wrote that immigration courts need not reopen "removal" - or deportation - proceedings on the grounds that an immigrant's attorney was incompetent. As a result, illegal immigrants and asylum seekers who lose deportation hearings because their attorneys fail to file legal papers on time, who do not show up for hearings or myriad other infringements lack recourse in immigration court.

The decision stems from three cases in which immigrants appealed deportation orders. In one, the lawyer of a Malian man who had overstayed his visa but married an American citizen neglected to file a legal brief in an appeal of a deportation order. In another case, the lawyer representing a Colombian who sought asylum under the United Nations convention against torture failed to file a legal brief. A coalition of law school clinics and immigration lawyers opposed the move, as did the American Bar Association, the top lawyers' guild in America.

"Immigrants, refugees and asylum seekers often are unfamiliar with our language, culture, and legal system, and as a result are especially vulnerable to being deceived by persons who are not authorized to practice law, or harmed as a result of mistakes by attorneys who lack sufficient familiarity with our nation's complex immigration laws," the American Bar Association's president, H Thomas Wells Jr, wrote to Mukasey.

Immigration courts have for decades operated under the premise that immigrants enjoy a constitutional right to effective counsel, immigration lawyers said. Criminal defendants whose lawyers fail to represent defendants at a basic level of competence may seek a new trial. Mukasey wrote that the US constitution affords a right to counsel, and hence a right to effective counsel, only in criminal matters. Immigration proceedings are civil matters, he wrote, and therefore that right does not apply.

In a brief opposing the decision, the American Immigration Law Foundation argued that in deportation proceedings, the government exercises its power to deprive immigrants of their liberty.

"The entire removal apparatus was created by the government; removal proceedings are initiated and conducted by the government; the government detains removable non-citizens until they can be removed, often throughout their proceedings; and removal is executed by the government," attorneys Nadine Wettstein and Emily Creighton wrote. "When a removal order is obtained in a process tainted by ineffective assistance of counsel," they continued, "it is the government's proceedings that have denied the respondent of constitutional rights".

A spokesman for the US justice department said in an interview that an immigrant denied a second hearing under Mukasey's decision will still be able to appeal to a higher-level panel of immigration judges, and ultimately to federal appeals courts.

The spokesman, Charles Miller, added that if Obama's nominee as attorney general, Eric Holder, disagrees with the decision he may overturn it.

"The attorney general based this on a review of court decisions, and I can't go beyond what he wrote in his opinion," Miller said.

Immigration lawyers on Thursday described the move as a last-minute blow to the US constitution by an administration that has for eight years sought to limit constitutional rights, for instance by arguing that prisoners at Guantánamo Bay have no access to US courts.

"It's a departure from long standing legal precedent," said David Leopold, a Cleveland, Ohio immigration attorney and vice-president of the American Immigration Lawyers Association. "In the waning days of this administration the attorney general has taken one more stab at a fundamental constitutional right, in this case the right to counsel for people who are facing the lifetime banishment from the United States."

Miller, spokesman for the justice department, disagreed.

"I can't tell you how long the attorney general was reviewing this - and those people working with him - but based on the opinion it looks like it was well thought-out before it was finally signed off and publicised," he said.