Tradeshift, a late-stage fintech startup that has raised over $1 billion in venture and debt, has dismissed its co-founder Christian Lanng, citing “serious allegations of sexual assault and harassment” and “gross misconduct on multiple grounds,” according to a company statement posted on Tuesday.

Lanng has vehemently denied the allegations. Tradeshift appointed former chief revenue officer James Stirk as interim chief executive.

Tradeshift — and its B2B fintech platform for payments, supply chain procurement and marketplace services between buyers and suppliers — has attracted investment from a wide range of investors, including strategic backers HSBC, Goldman Sachs, American Express and Intuit. Most recently, HSBC invested $35 million in July.

A spokesman said Goldman Sachs Group sold its shares in 2021. HSBC declined to comment on recent events.

Tradeshift’s statement said the company became aware of the allegations in late August and dismissed Lanng on September 1. The U.S.-Danish company said it has set up a “dedicated and anonymous whistle-blowing line” for its 800 employees.

In August, Lanng, while still running Tradeshift, launched a separate venture called Beyond Work, which describes itself as a “human-first interface to automate anything with multiplayer AI.” It has raised $2.5 million in pre-seed funding led by Moonfire Ventures, with co-investment from MIT-affiliated fund E14 and is currently waitlist-only. TechCrunch reached out to Moonfire for comment and we will update this post with any reply we receive.

In a statement sent to TechCrunch, Lanng said: “I refute the statement made this week by Tradeshift. There has never been an HR case, complaint or formal allegation filed against me at Tradeshift. The board includes long term members who would have been aware of any such claims, so the statement that the board recently became aware of anything is not true.”

Lanng added: “I have given the current management and new board every opportunity to move on peacefully. This would still be my preference, but I am now taking advice on my next steps.”

Lanng claimed the allegations stemmed from a breakdown in negotiations over his and others’ exits from Tradeshift. “Multiple co-founders are leaving Tradeshift after being in active discussion about our exit post HSBC deal when the board moved to dismiss me,” he said.

In an apparently unrelated development, Tradeshift co-founder and former head of platform Mikkel Hippe Brun posted on LinkedIn on Tuesday that he had left Tradeshift to work on another startup. TechCrunch has reached out to him for comment.

A spokesperson for Tradeshift said the company was not responding to Lanng’s statements beyond what it had already posted on its web site. TechCrunch has not yet been able to independently substantiate Tradeshift’s allegations against Lanng. Three women contacted individually by TechCrunch, who have worked or are working at Tradeshift, have voiced their support of him to us.

Lanng formed Tradeshift in 2005 with Hippe and Gert Sylvest, originally under the name EasyTrade. It has been valued as high as $2.7 billion, in 2021.