Conservatives continue to wage war over the future of the Republican Party, with Media Research Center president Brent Bozell and several other activists penning a letter discouraging donors from giving money to Karl Rove's new political group.

Rove has been the focus of conservative anger for weeks following the announcement of Conservative Victory Project, a new group he is launching with the help of the allies behind his Crossroads political groups. According to the New York Times, the group will seek to “recruit seasoned candidates and protect Senate incumbents from challenges by far-right conservatives and Tea Party enthusiasts.”

The letter, flagged by TIME reporter Zeke Miller, is signed by Bozell, Tea Party Express chairman Amy Kremer, Citizens United president David Bossie, Family Research Council president Tony Perkins, and a handful of other conservative activists who claim to represent “millions of grassroots conservatives.”

Addressed to “Top Crossroads Donors,” the letter rips Rove's Crossroads political groups for supporting moderate candidates and having “squandered hundreds of millions of dollars in what were arguably the most inept campaign advertising efforts ever.”

It continues:

Mr. Rove and his allies must stop blaming conservatives for his disastrous results. It is time for him to take ownership of his record. He must also stop posturing himself as a conservative: his record supporting wasteful government spending and moderate candidates over conservatives spans decades. No matter how he positions himself in this attempt at damage control, Mr. Rove's efforts will not elect the type of leaders who will come to Washington to fight for conservative principles. In fact, they are likely to stifle the emergence of candidates like Marco Rubio, Pat Toomey, and Rand Paul. Further, the model that will be employed by the Conservative Victory Project has proven to be ineffective and a waste of political resources.

In recent weeks, Rove has been labeled by conservative media figures as (among other pejoratives) a “propagandist” and “a total loser.” Conservatives have also branded his new group “absolutely repulsive,” and “an incumbency protection racket.”

Last month, after a spokesman for one of Rove's Crossroads groups labeled Bozell a “hater” for his criticism of Republican leaders, Bozell's allies -- including several of the same people who signed the latest letter -- wrote a letter demanding the aide's firing. In the letter, the activists lauded Bozell for being the nephew of conservative luminaries like William F. Buckley and called him “a beloved and critically important player in American history.”