Although qualified, Miers is ''clearly not the most qualified person for the job,'' Lott, said on MSNBC on Wednesday.
''I'm not satisfied with what I know. I'm not comfortable with the nomination, so we'll just have to work through the process in due time,'' he said.
Bush is facing opposition to the nomination of Miers, the White House counsel, from some in his Republican base. If confirmed, she would replace Justice Sandra Day O'Connor, who announced her retirement plans earlier this year and is often a critical swing vote on the high court. Many are disappointed that the president did not pick an experienced judge with a clear conservative record.
Sen. Sam Brownback, R-Kan., a conservative and possible 2008 presidential candidate, said a day earlier that he is not yet confident that Miers has a proven track record and that questions about her views on the Constitution need to be answered.
In addition, the conservative New Hampshire Union Leader newspaper said in an editorial Wednesday that Miers ''is no more or less qualified to sit on the Supreme Court than thousands of other attorneys with similar career highlights'' and that her nomination is an example of cronyism.
And conservative syndicated columnist George Will said, ''There is no evidence that she is among the leading lights of American jurisprudence, or that she possesses talents commensurate with the Supreme Court's tasks.''
Will also said Bush can't be trusted to make a sound pick because ''he has neither the inclination nor the ability to make sophisticated judgments about competing approaches to construing the Constitution.''
At the White House, spokesman Scott McClellan said Miers has earned the respect and admiration of the legal profession and will earn the same sentiment from the American people.
''She is someone who is deeply committed to our Constitution and our laws,'' he said, adding she is firmly committed to the same kind of judicial philosophy that the president believes in. That is a philosophy that is based on strictly interpreting our Constitution and our laws.
The 60-year-old Miers has served Bush in a variety of private, political and government roles. Most have been done in a way that does not shed much light on her judicial or political philosophy. She came to Washington with Bush in 2001 as staff secretary and became deputy chief of staff before becoming the top White House lawyer when Alberto Gonzales became attorney general.
On Wednesday, Miers continued her meetings with key lawmakers on Capitol Hill, including a one-hour meeting with Sen. Patrick Leahy, D-Vt., ranking member of the Senate Judiciary Committee.
After the exchange, Leahy said that remarkably little is known about Miers and that such a ''sparse record'' requires the White House to cooperate in releasing documents from her tenure there. He pointed out that the White House released 60,000 pages of information on John Roberts, recently confirmed at the nation's chief justice.
''The whole Senate needs to know more about the nominee. The American people have to know more about her,'' Leahy told reporters. ''No Supreme Court nomination should be conducted with winks or nods. It should be out in the open.''