A third formal complaint has been made against the former Labour MP Geraint Davies who was suspended over allegations of inappropriate behaviour, Sky News understands.
Mr Davies was suspended by the party last week after a number of accusations surfaced in the media. He has denied the claims.
Two formal complaints were made by women over the following two days, but Sky News now understands a third has been submitted.
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It comes as Sir Keir Starmer told reporters he was "determined to tackle" sexual harassment within Labour.
Speaking before the news broke, the party leader said: "I'm obviously concerned about any allegations of this nature, whether that's in the Labour Party, in parliament or anywhere across the country and [we're] determined to tackle them.
"That's why we've changed our processes to hopefully give people the confidence to come forward.
"The most important thing I can say is that to anybody who has concerns or allegations or information, I want them to come forward, I want them to feel confident to come forward, and if they're able to do so they'll be supported and we'll get to the bottom of this."
Mr Davies was first elected as an MP in 1997 and now represents Swansea West.
After the allegations came to light in a report by Politico published on Thursday, Labour "administratively suspended" him from the party pending an investigation into reports of "incredibly serious allegations of completely unacceptable behaviour".
The 63-year-old politician has denied the claims and told the website: "I don't recognise the allegations suggested and do not know who has made them.
"If I have inadvertently caused offence to anyone, then I am naturally sorry as it is important that we share an environment of mutual and equal respect for all."
In the wake of the Davies claims, a Labour Party spokesperson said: "We would strongly urge anyone with a complaint to come forward so that allegations can be swiftly and fully investigated and action taken.
"The party has ensured that there is a wide range of support available to complainants, to provide confidence and confidential guidance throughout the disciplinary process."