WASHINGTON — Senate Republicans continued a campaign to delay confirmation of President Barack Obama’s second-term Cabinet-level nominees on Thursday, blocking a committee vote on Gina McCarthy, the president’s pick to lead the Environmental Protection Agency.
The action came a day after Republicans on the Health, Education, Labor and Pensions Committee threw a wrench in the nomination of Thomas E. Perez to be labor secretary, delaying it for at least a week.
In both cases, Republican committee members said the nominees had failed to adequately respond to their questions.
The eight Republicans on the Environment and Public Works Committee, led by the ranking member Sen. David Vitter of Louisiana, boycotted a committee meeting to protest what they called McCarthy’s ‘‘unresponsive answers’’ to more than 1,000 written questions about EPA policies and internal practices.
Democrats were unable to muster a majority to move the nomination without any Republicans present and were left to fulminate in a near-empty committee room over what several of them called Republican obstructionism. Committee Democrats are likely to regroup and try to approve McCarthy’s nomination along party lines, but it is unclear whether they could clear a 60-vote threshold on the Senate floor.
Sen. Harry Reid, D-Nev. and the majority leader, accused Republicans of using procedural roadblocks and stall tactics to deny confirmation to qualified nominees.
''This type of blanket, partisan obstruction used to be unheard-of,’’ Reid said on the Senate floor. ‘‘Now it has become an unacceptable pattern.’’
He vowed that the Senate would have an opportunity to vote on the nominations of Perez and McCarthy.
Sen. Barbara Boxer, D-Calif., who leads the environment panel, said that McCarthy was one of the most qualified nominees ever named to lead the EPA.
McCarthy, who grew up in Canton, is a graduate of the University of Massachusetts Boston and Tufts University. A career public servant, she is currently head of the agency’s office of air and radiation, a post to which she won easy Senate confirmation in 2009. She previously served as a top environmental regulator in Connecticut and Massachusetts, working for Democratic and Republican governors.
She is perhaps best known in Massachusetts for her work in crafting tough air pollution rules that cleaned up the “Filthy Five” — the state’s dirtiest coal- and oil-fired power plants.
“Gina McCarthy deserves a vote,’’ said Boxer, visibly angry. ‘‘I have delayed a vote for three weeks. I was assured by Sen. Vitter that once he received answers to 1,000 questions — a record-breaking number — they would allow us to move forward with the vote.’’
Boxer and other committee Democrats noted that Republican members had submitted 1,079 questions to McCarthy, compared with 157 total questions for Obama’s first EPA administrator, Lisa P. Jackson, and 305 for Michael O. Leavitt, who served in the post under President George W. Bush.
Democrats boycotted a vote on Leavitt’s nomination in October 2003, saying he had failed to adequately answer their questions on environmental policy. The move forced a two-week delay in his confirmation.
Vitter, in a letter to Boxer and at a news conference Thursday, said that Republicans were not seeking to obstruct the nomination or harass the nominee.
''These requests are all about openness and transparency and things required by law,’’ Vitter told reporters. ‘‘We’re not asking the Obama administration to walk away from their views on carbon or anything else.’’
He said that the EPA had been unresponsive to Freedom of Information Act requests, that it had failed to provide scientific data supporting regulations and that top officials had used aliases in email addresses, a practice now under review by the agency’s inspector general.
Boxer said she intended to press for a vote on McCarthy, which she can do if all 10 Democratic members of the committee appear in person. Sen. Max Baucus of Montana was at another hearing, and did not attend Thursday’s meeting, nor did Sen. Frank R. Lautenberg of New Jersey, who has been largely absent from the Senate in recent weeks because of health concerns.
''It was not my intention to vote this out with just Democrats,’’ Boxer said. ‘‘I am asking my Republican colleagues to come home, come back to your responsibility. If you want to be here and vote no, be here and vote no. That is your prerogative. But vote.’’
Jeremy W. Peters contributed reporting.