The SP intervenes in the youth branch RED, because former SP member Olaf Kemerink has become president of the club.
Kemerink was recently expelled by the mother party.
RED no longer receives money from the board and the party also suspends support at, for example, administrative level.
Kemerink was elected RED chairman on Sunday, with three quarters of the votes.
This happened shortly after he was expelled from the SP for allegedly holding violent communist views.
The party rules stipulate that you can only be a member of RED if you are also a member of the SP.
"The party board of the SP has determined that the situation that has arisen is in violation of the rules and therefore we cannot take responsibility for it", says SP chairman Jannie Visscher.
The board will soon be told what the intervention means for RED in practice, she promises.
The SP says it remains open to a discussion with RED about the situation.
SP expelled 'radicalized attic communists'
Kemerink was expelled from the party by the board together with five other SP members.
According to the party, it concerns a group of "radicalized attic communists" with ties to the Communist Platform and the Marxist Forum.
The expelled members see this as movements within the party, but the SP itself sees it as parties in itself and does not accept double membership.
The SP board previously told
that the Communist Platform first simply discussed Marxist ideas, but is now occupied with "very scary things".
"They want to arm the population to start a civil war".
The board also fears that the more radical wing is trying to take over the party.