COLOMBO, Sri Lanka (AP) — Sri Lankan opposition lawmakers have withdrawn from a committee looking into impeachment charges against the country's chief justice, saying the process is flawed and unfair.

The United States added to the criticism, saying the impeachment trial of Chief Justice Shirani Bandaranayake is "part of a disturbing deterioration of democratic norms in Sri Lanka."

The government of President Mahinda Rajapaksa accuses Bandaranayake of having unexplained wealth and misuse of office, but she denies any wrongdoing. The opposition says the impeachment is a move by the government to stifle judicial independence and concentrate more powers in the hands of Rajapaksa.

A parliamentary committee with seven government lawmakers and four opposition party members was appointed to look into the charges against the chief justice. Bandaranayake said Thursday that she would not appear before the committee again because she will not get a fair hearing.

On Friday, lawmaker John Amaratunga told reporters that four opposition lawmakers who sat on the committee walked out because they could not be party to an unfair process.

The lawmakers said the government members had used their numerical majority to reject what they said were reasonable demands to establish a procedure for the inquiry, and give Bandaranayake an opportunity to cross-examine her accusers and enough time to study the 300 documents relevant to the case.

The opposition said too many of the accusers and judges in the case were from the same group — government lawmakers, whereas in other countries such inquiries are assigned to separate legal professionals appointed by parliament.

With no clear precedence and no agreed procedure, the inquiry was held in an ad-hoc manner, they said.

They also said that the government lawmakers treated Bandaranayake in an insulting and intimidating manner, and that their remarks clearly showed they had already found her guilty.

The impeachment is a culmination of a months-long dispute between the parliament and the judiciary.

Bandaranayake began to be heavily criticized by the government after she ruled that legislation giving sweeping powers to the economic development minister violated the constitution. The minister is Rajapaksa's brother.

The case has drawn international attention.

In a statement Friday, State Department spokesman Mark Toner said the U.S is deeply concerned about actions surrounding the impeachment trial and urged the government to ensure due process.

"These latest developments are part of a disturbing deterioration of democratic norms in Sri Lanka, including infringement on the independence of the judiciary," Toner said, calling for the government to uphold the rule of law and democratic governance.

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Associated Press writer Matthew Pennington in Washington contributed to this report.