Paul "PK" Kemsley is clapping back at his estranged wife ... saying Dorit Kemsley 's claim he hasn't reached out once to see their kids during the "RHOBH trailer is nonsense.

Dorit's allegation landed in the explosive new Season 15 trailer, where she suggested to Mauricio Umanksy during a sit-down dinner that PK has been completely absent from their children's lives. The estranged pair share two kids ... 11-year-old son Jagger and 9-year-old daughter Phoenix .

TMZ caught up with the music manager Tuesday in Beverly Hills, where PK shut the claim down with a brief but firm response -- "It's not true."

As we previously reported ... Dorit formally filed to end the marriage earlier this year, filing for sole legal and physical custody. The couple, who wed in March 2015 and

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