Although SAG and AFTRA will have to band together soon for tough contract negotiations with studios and nets, internecine warfare has broken out between them over contract poaching, among other issues.

The Screen Actors Guild has taken a blistering shot at the American Federation of Television & Radio Artists for poaching contracts on cable shows, prompting AFTRA to accuse SAG of trying to muscle its way into control of the smaller union.

SAG topper Doug Allen has written a 12-page letter to members in the newest issue of the guild’s quarterly magazine, detailing the potential lost revenues to actors when AFTRA negotiates contracts at less-favorable rates than SAG in areas of shared jurisdiction.

The letter in the fall issue of SAG Actor, which began hitting member mailboxes Wednesday, accuses AFTRA of shilling for producers and undermining the bargaining position at next year’s negotiations with the Alliance of Motion Picture & Television Producers. The SAG-AFTRA film-TV contract expires June 30.

“AFTRA has recently recorded significant growth in the area of one-hour scripted basic cable,” Allen wrote. “This has historically been work within the Screen Actors Guild’s jurisdiction and appears to be growth obtained at a disadvantage to performers who have been covered by SAG’s contractual provisions. Not only is the work not performed under our contracts, but the AFTRA contracts, typically negotiated on a show-by-show basis, seem more advantageous to producers than Screen Actors Guild contracts would be.”

AFTRA president Roberta Reardon fired back in a letter to members sent out Wednesday in which she accused Allen and SAG leaders of manipulative attacks and fear-mongering. She also delivered a salvo of her own, asserting that the move is designed as part of plan for SAG to take over AFTRA.

“There is another thinly veiled campaign supported by some SAG paid staff and others to raid another union — the cardinal sin of treachery within the labor movement,” Reardon added.

AFTRA has long contended that SAG’s beef isn’t legitimate — that it’s entitled to organize any show within its jurisdiction, and that signing deals at lower terms is preferable to the shows being shot non-union or in Canada.

SAG reps about 120,000 thesps, while AFTRA has about 70,000 members; about 40,000 performers belong to both unions. In the letter, Allen asked SAG members to ask for SAG contracts when they book basic cable deals.

“If you’re a dual cardholder, let your AFTRA representatives know that you support cooperation and collaboration,” he added.

The spat comes with the two unions expected to begin joint negotiations on a new film-TV contract early next year. Allen, who’s teamed with SAG president Alan Rosenberg to press AFTRA on the jurisdictional front, asserted that AFTRA’s making it more difficult to present a united front at the bargaining table.

“Lowering the bar through competition between unions is rarely a good idea,” Allen wrote. “Doing so now is particularly ill considered and sends a divisive message to producers as we prepare for landmark negotiations in 2008.”

Allen’s letter contains multiple charts showing that the pay actors receive is as much as 53% less on such AFTRA shows as “Army Wives,” “The Minor Accomplishments of Jackie Woodman” and “Dirt” due to AFTRA’s decision to make deals with smaller residuals.

It also details the differences between the SAG and AFTRA health and retirement plans, noting that the SAG health plan provides full dependent coverage for as little as $10,000 in annual earnings vs. $30,000 for the AFTRA plan.

Allen’s missive is reopening the rift between the Hollywood branch of SAG — which reps 60% of SAG’s 120,000 members — and the elected reps in New York and regional branches.

Those two boards sent Allen a letter two weeks ago that labeled his missive “inflammatory” and “misleading.” The reps also asserted Allen had overstepped his authority by not seeking the “express consent” of the national board and issued a vague threat that they would have no choice but to respond — without specifying how.

It’s highly doubtful that SAG’s board would seek Allen’s ouster since the Hollywood branch has control of the board room.

The two unions have a history of enmity over jurisdictional issues that dates back to their origins in the 1930s. Earlier this month, more than 240 supporters of a SAG-AFTRA merger launched a PR campaign to revive the push to combine the performers unions.

AFTRA tried unsuccessfully to merge with SAG in 1999 and 2003; in both cases, AFTRA members backed the deal, but SAG members voted it down amid concerns that SAG would lose its autonomy and that combining the respective pension and health plans would be difficult.

Both unions have made moves recently that may make it more difficult to present a united front next year. SAG, long perturbed that AFTRA has 50% of the seats on the negotiating committee bargaining despite generating less than 10% of the earnings, is planning to institute bloc voting among its members on the committee; AFTRA’s been seeking to become a direct affiliate of the AFL-CIO by withdrawing from another labor org — the Associated Actors and Artistes of America, in which it’s partnered with SAG and other entertainment unions.