Conservative Republicans in the House are seriously concerned with reports that House Speaker John Boehner has abandoned GOP principles in his behind-closed-doors fiscal cliff negotiations with President Barack Obama by offering a tax rate increase.

Kansas Republican Rep. Tim Huelskamp told Breitbart News that the reports that Boehner has caved are troubling for the future of the GOP and for the economy.

“If the offer is in fact true – and we’re still hearing this just from anonymous ‘sources’ – then Speaker Boehner must have forgotten that nearly all Republican House members, including himself, campaigned on opposing just such tax increases,” Huelskamp said in an email. “Caving into President Obama’s tax increase demands would not only seriously damage the economy, but also the future of the Republican Party.”

Politico first reported late Saturday evening that Boehner had offered in his secret meetings with President Obama that he’d allow a tax increase for “millionaires.” Obama reportedly rejected the offer, claiming Boehner hadn’t caved on Republican principles enough.

“Speaker John Boehner has proposed allowing tax rates to rise for the wealthiest Americans if President Barack Obama agrees to major entitlement cuts, according to several sources close to the talks,” Politico reported. “It is the first time Boehner has offered any boost in marginal tax rates for any income group, and it would represent a major concession for the Ohio Republican. Boehner suggested hiking the Bush-era tax rates for top wage earners, including those with annual incomes of $1 million or more annually, beginning Jan. 1, two sources said.”

Since the original Politico report, the Associated Press, Fox News and others have confirmed Boehner’s offer to raise tax rates in violation of basic conservative principles. Then, late Sunday evening, the Washington Post reported that Boehner has caved even more. According to the Post, Boehner offered Obama that he’d give up all Republican leverage with regard to the debt ceiling for a whole year.

“House Speaker John A. Boehner has offered to push any fight over the federal debt limit off for a year, a major concession that would deprive Republicans of leverage in the budget battle but is breathing new life into stalled talks over the year-end ‘fiscal cliff,'” the Washington Post wrote late Sunday.

Given multiple opportunities to do so by numerous news organizations including Breitbart News, Boehner spokesman Michael Steel would not refute the reports that his boss caved in secret negotiations.

Instead, Steel allowed the reports to stand adding that he won’t talk about what the speaker and the president are discussing behind closed doors. “The lines of communication remain open, but there is no agreement, nor is one imminent,” Steel said, according to Politico.

“We have not commented on the content of private discussions, and we’re certainly not going to comment on rumors,” Steel added, according to BuzzFeed’s Zeke Miller.

Steel wouldn’t explain to Breitbart News why Boehner made the decision to conduct such negotiations in private. He could, of course, take the negotiations public – a move that would force him and the president to justify any decisions to the American people.

According to Louisiana Republican Rep. John Fleming, such an increase in tax rates would be the first time in American history a GOP-led House of Representative ever raised tax rates. “For nearly a century, Republican-controlled Houses held the line on tax rates, a Republican coup de pointe to Democratic tax-increase parries,” Fleming wrote in a Washington Times op-ed last week. “Here’s the question for my fellow Republicans: Do we want to be the first-ever GOP House majority to raise federal marginal income tax rates?”

In response to the reports that Boehner has caved, Fleming told Breitbart News that he’s troubled Republicans keep offering specifics while Democrats and Obama haven’t offered any legitimate specific plans to deal with the fiscal cliff. “Republicans continue to offer specifics on tax increases and Obama refuses to offer anything on entitlements,” Fleming said in an email. “Where is the balanced approach?”

While conservatives in the House wonder why Boehner has abandoned GOP principles with this tax increase offer, Senate Republicans appear ready to break with the Speaker of the House as well. Don Stewart, a spokesman for Senate Minority Leader Mitch McConnell, told reporters on Friday that the top Senate Republican won’t support what Boehner is reportedly offering.

“Senator McConnell does not advocate raising taxes on anybody or anything,” Stewart said. “Despite the president’s failure to lead or to offer any real solutions to the last four years of trillion-dollar deficits, Republicans will continue to look for ways to protect American families and jobs while strengthening entitlement programs.”

Asked if House Majority Leader Eric Cantor agrees with Boehner on tax increases, assuming the reports are true, Cantor spokesman Rory Cooper refused to answer. “There is no agreement, nor is one imminent,” Cooper told Breitbart News. “Not going to comment on rumors.”