Rep. Paul Ryan's (R-Wis.) political group went on the attack Monday against AARP, calling one of the most powerful lobbies a "left-leaning pressure group."

Ryan's Prosperity PAC sought to push back on attacks by AARP against the House Budget Committee chairman's 2012 budget, specifically its proposed changes to Medicare.

"Last week, the American Association of Retired Persons (AARP), a left-leaning pressure group with significant business interests in the insurance industry, launched a national ad campaign that intentionally misleads seniors about the Medicare debate," wrote Pat Shortridge, a senior adviser to Ryan's PAC, in an email to supporters.

Ryan's Medicare proposal has been a particular point of criticism by Democrats and groups on the left, which say that the Medicare plan would significantly revamp the entitlement program to the detriment of seniors. Democrats have homed in their attacks against that part of the Ryan budget, which has sparked some degree of heartburn among Republicans.

AARP launched ads last week warning against "harmful cuts" to Medicare and Social Security it said Republicans favored.

Rep. Dave Camp (R-Mich.), the chairman of the House Ways and Means Committee, expressed skepticism about advancing Ryan's plan through the committee when it would likely be dead-on-arrival in the Democratic-led Senate. But senior Republicans including House Speaker John Boehner (R-Ohio) and Camp rallied around Ryan's proposal in a joint statement on Friday.

Still, Ryan's allies are stepping out onto tricky turf by challenging AARP, one of the largest and most influential lobbying groups in Washington, as well as a large voting bloc both parties seek out every election cycle — that represents senior citizens, no less.

"Unfortunately, Washington’s special interest groups, like the AARP, have decided to play politics," Shortridge wrote. "We either need them to have a serious conversation or get out of the way."