A group of Republican Senators who want to prevent any recess appointments have asked Speaker John Boehner (R-Ohio) to block any resolution that would allow the Senate to adjourn.

The Senate is scheduled to take a weeklong Memorial Day recess next week, while the House stays in session. Sens. David Vitter (R-La.) and Jim DeMint (R-S.C.) and 18 others pointed out in a letter Wednesday that neither chamber can adjourn for more than three days without the consent of the other.

President Barack Obama “has used recess appointments to fill powerful positions with individuals whose views are so outside the mainstream that they cannot be confirmed. … We urge you to refuse to pass any resolution to allow the Senate to recess or adjourn for more than three days for the remainder of the president’s term,” the Senators wrote.

Consumer Financial Protection Bureau adviser Elizabeth Warren and National Labor Relations Board member Craig Becker — both unpopular with the Republican caucus — were appointed during recesses, as were other “controversial nominations,” such as James Cole at the Justice Department and Philip Coyle at the Department of Commerce, Vitter said in a news release that accompanied the letter.

“Obama has a poor track record of appointing some really controversial characters during congressional breaks,” Vitter added.

Wednesday’s letter is the most recent effort made by Republicans to stymie the confirmation of Obama’s nominees.

Sen. Tom Coburn said last week that he would fight a bipartisan effort to streamline the nominations process. The Oklahoma Republican opposes a bill that would eliminate the confirmation process for more than 200 executive branch appointees and a Senate rules change that would expedite the confirmation of nearly 250 others.

Also on Wednesday, Berkeley law professor Goodwin Liu asked the president to withdraw his nomination to the 9th U.S. Circuit Court of Appeals after Senate Republicans filibustered his nomination, the first successful filibuster of a judicial nominee in six years.