MP Jonathan Edwards has been suspended from Plaid Cymru for 12 months after he accepted a police caution.
The Carmarthen East and Dinefwr MP was arrested on 20 May on suspicion of assault.
On Wednesday Plaid Cymru’s disciplinary panel suspended him from the party saying it was a “serious matter”.
The 44-year-old MP, who has described the incident as the “biggest regret” of his life, said he fully accepted the decision of the panel.
Mr Edwards referred himself to the party’s internal disciplinary committee following his arrest, and had the whip withdrawn.
Now he will be suspended from the party for 12 months, meaning he will be effectively sitting as an independent MP.
In a statement the disciplinary panel said: “Any lifting of the suspension after 12 months is dependent upon Mr Edwards appearing before the panel to demonstrate that he has undertaken a period of self-reflection and learning to address his actions”.
At the time of the caution Mr Edwards said: “I am deeply sorry. It is by far the biggest regret of my life.”
A statement on behalf of his wife, Emma Edwards, said: “I have accepted my husband’s apology.
“Throughout the decade we have been together he has been a loving and caring husband and father.”
Plaid Cymru said Mr Edwards had “co-operated fully with the investigation” by the panel.
The party added: “If Mr Edwards fails to abide by the terms of the suspension he will be excluded.”
Alun Ffred Jones, the chairman of Plaid Cymru, said the party “condemns any behaviour that falls below what is expected of our membership”.
“The speed and outcome of the disciplinary process reflect the seriousness with which the party has dealt with this matter,” he said.
“All forms of harassment, abuse and violence are unacceptable, and this has been reflected in the verdict.”