Spokesperson for the Green Party Gustav Fridolin told Swedish Radio's P1-morgon programme that he only found out about the allegations and inquiry last week.
The Green Party is the junior partner in Sweden's coalition government.
The accused MP had been reported internally for unwelcome advances and sexual harassment for over ten years. On one occasion, he was reported to the police.
Swedish newspaper Dagens Nyheter spoke to roughly twenty party members who say they witnessed the man's inappropriate behaviour, including one who aaccused him of assaulting her baby.
Fridolin said that this needed to lead to a serious change. "We've made sure that there's more awareness within the party about protocols on reporting people, when you witness or experience something that's not right," he added.
The accused party member was able to stay on despite being reported multiple times, first as a local position, and later as an MP. According to Dagens Nyheter, there had been a number of attempts by party secretaries and nomination committees to prevent him from being elected.
The MP in question first took a "timeout" and has now left the party and will sit in the Riksdag as an independent until the 2018 election, reports Dagens Nyheter.