It means the party thinks they have cases to answer and could potentially lead to their permanent sacking from membership, although the party cannot fire them as MPs.
Mr Lewis was suspended from Labour in November following claims that a woman had accused the Bury South MP of touching her leg and inviting her to his house when she was 19 at Labour Party event in 2010.
Former minister Mr Lewis responded to the accusation by saying he had never forced himself on women but understood that “a few had claimed that my behaviour made them feel uncomfortable.
“I have on occasion asked women I work with out for drinks or dinner, or developed strong feelings for them, and I am genuinely sorry if this was unwelcome or inappropriate in the circumstances, and caused anyone to feel awkward.”
A Labour spokesman said: “After consideration of statements provided by the complainant and the respondent, the National Executive Committee’s sexual harassment panel has agreed that on the balance of the evidence the matter should be referred to a full hearing of the national constitutional committee.”
Mr Lewis said he would “continue to cooperate fully with any investigation”.
Mr Hopkins has also been referred to the NCC.
Ava Etemadzadeh, 27, claims the 76-year-old Luton North MP acted inappropriately and sent her suggestive text messages after they met at a student event in 2014, which he categorically denies.
The long-serving left-wing pro-Brexit campaigner was reprimanded after she first complained in 2015, but was later briefly promoted to Jeremy Corbyn’s shadow cabinet.
Mr Hopkins has been suspended since November pending investigation of Ms Etemadzadeh’s complaint and separate allegations by MP Kerry McCarthy of unwanted attention over a number of years.
Yesterday FRI he said: “This issue needs to be dealt with by due process and I am happy to go to the NEC to clear my name.”
Last month, former Jeremy Corbyn ally Clive Lewis was cleared of groping a female Labour member after the party’s harassment panel ruled “that on the balance of the evidence the matter should not be referred to a full hearing” of the NCC.