* Opposition members of an impeachment panel withdraw
* Chief justice asks for independent impeachment panel
* US urges Sri Lanka to ensure transparency, rule of law
By Shihar Aneez and Ranga Sirilal
COLOMBO, Dec 7 (Reuters) - Sri Lanka's opposition walked out of parliament on Friday protesting what it called unfair impeachment proceedings against the country's chief justice and its party members left the select committee which is carrying out the investigation.
The opposition's reaction came a day after Shirani Bandaranayake, Sri Lanka's first female head of the Supreme Court, withdrew from the impeachment process because, her lawyers said, she had lost faith in the proceedings.
Tension has risen between the judiciary and government since President Mahinda Rajapaksa's ruling party filed a motion against Bandaranayake in parliament last month.
The United States, the United Nations and the Commonwealth have raised concern about the process and have called on the government to ensure the independence of the judiciary.
Parliament Speaker Chamal Rajapaksa, the president's elder brother, appointed an 11-member select committee, seven of them from the ruling party, to investigate 14 charges against Bandaranayake ranging from not disclosing her wealth to professional misconduct.
The four opposition members on the impeachment committee withdrew from it on Friday citing injustice and the entire opposition party left the parliamentary chamber en masse.
"We can't be party to injustice," John Amaratunga, an opposition legislator in the impeachment panel told reporters.
He said the ruling party members of the panel had rejected opposition requests for a fair time for the chief justice to cross-examine witnesses.
The panel also rejected a chief justice request to allow Commonwealth and local observers, her lawyers said.
The absence of the chief justice and the four opposition members will not stop the panel proceeding with its investigation and impeaching Bandaranayake if she is found guilty as the quorum needed is only six, a panel member said.
On Thursday, Bandaranayake's lawyers said the impeachment committee handed over hundreds of documents and asked the chief justice to prepare for the trial with less than 24 hours notice and rejected her request to cross-examine the witnesses.
"It is regrettable that the committee is ignoring salient provisions of the law and requirements of natural justice in the conduct of this inquiry," Amaratunga said.
Bandaranayake's lawyers on Friday requested the speaker to appoint an impartial committee to continue the impeachment.
"In the interests of the judiciary, country, and client, we request that our client be given the opportunity of vindicating herself before an independent and impartial tribunal," the legal firm appearing on behalf of the justice requested in a letter.
Minister of Higher Education S.B. Dissanayake said the walk outs by the opposition and chief justice were tactical moves to destabilise the parliament select committee proceedings.
The United States on Friday raised concerns over the impeachment process.
"We urge that the government of Sri Lanka and the parliamentary select committee investigating the chief justice ensure any investigation be conducted transparently, guarantee due process, and is conducted in accordance with the rule of law," the U.S. embassy in Colombo said in a statement.
Bandaranayake recently came under criticism from government supporters for ruling against a bid by the central government to take control of an 80 billion rupees ($614.20 million)development budget, saying it had to be approved by nine provincial councils.
The ruling angered the government and its backers, some of whom accused the judiciary of overstepping its authority before moving the impeachment motion. (Writing by Shihar Aneez; Editing by Jon Hemming)