Suffolk County Police Commissioner Timothy Sini received a major boost in his bid for district attorney Wednesday, as the county’s major police unions and the group representing East End and village police endorsed him.

Also, Michael Long, state Conservative Party chairman, in an unusual move assailed Suffolk Conservatives for backing Sini, a Democrat, after he accepted the endorsement of the Working Families Party.

Long said the Working Families Party “is violently opposed to everything the Conservative Party stands for,” and urged Sini to decline the Working Families line.

Noel DiGerolamo, president of the Suffolk Police Benevolent Association, announced the endorsement by his union, which also represents probation officers and park police.

The Superior Officers Association, which represents police supervisors, and the Suffolk County Police Conference, which represents officers in other police agencies throughout the county, also endorsed Sini.

In addition, the unions endorsed state Sen. Phil Boyle (R-Bay Shore) for Suffolk County sheriff.

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“After careful consideration of the candidates left in the race, there was little doubt in our minds these are the individuals best suited to hold those positions and who will best serve county residents,” DiGerolamo said.

The union endorsements are significant not only because of the size of their memberships, but also because the unions have mailing lists of officers serving in other metropolitan area police agencies who live in Suffolk.

More important, the groups have an independent expenditure arm, the Long Island Law Enforcement Foundation, which has spent more than $2.8 million on local political campaigns in the five years since its formation in 2011.

“I think it speaks volumes of the great work Tim has done as police commissioner,” said Richard Schaffer, Suffolk Democratic chairman. “Normally, there is friction between the commissioner and the police force . . . ”

Sini did not return calls for comment. But his campaign chairman David Kelley said, “We welcome everyone’s endorsement. When you talk about a law enforcement spot, it’s not politics as usual. You are talking about professionalism, integrity and doing the right thing.”

Long said there is no party rule barring a local party from making such an endorsement but called the situation untenable.

“It’s evident the Working Families Party is just looking for power. Maybe some of my own people are making the same mistake,” Long said in an interview.

“I have vocally made it very clear to the leaders of the party, to the state executive committee, to county leaders . . . I just cannot accept how anyone can take the Working Families Party endorsement and Conservative Party endorsement,” Long said.

Frank Tinari, Suffolk Conservative chairman, could not be reached for comment Wednesday night.

But Bill Lipton, state director of the Working Families Party, said his party “proudly stands by our endorsement” in the Suffolk district attorney’s race.

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“As far as the Suffolk County Conservatives’ criteria for choosing their nominee, you’ll have to ask them,” Lipton said.