Wynn Resorts has denied multiple allegations of sexual harassment and assault by its founder, Steve Wynn, which were detailed in a Wall Street Journal report that sent shares of the casino tumbling 9% on Friday.

The paper reported that a number of women say they were harassed or assaulted by the casino mogul, who is also finance chair of the Republican National Committee.

One case led to a $7.5m settlement with a manicurist, the Journal reported. Its detailed report relied on interviews with dozens of people who corroborated a decades-long pattern of sexual misconduct with female employees.

The company said it was committed to operating with the “highest ethical standards and maintaining a safe and respectful culture”.

According to campaign finance records, Wynn also donated to Greg Gianforte, the Republican congressman who assaulted Guardian reporter Ben Jacobs on the eve of the Montana special election. Wynn gave Gianforte a maximum individual contribution of $2,700 on 25 May 2016, the day after he assaulted Jacobs.

In a printed statement, Wynn Resorts said the allegations were part of a smear campaign related to divorce proceedings involving Wynn’s ex-wife.

Wynn himself said: “The conduct of Elaine [Wynn] during the course of the pending lawsuits has been shocking and deeply disturbing to me personally and as the CEO of Wynn Resorts.”

The RNC did not respond to requests for comment.

The Democratic national committee condemned the RNC Friday for remaining “silent” in the wake of the Wynn revelations, while also pointing out the group had backed Alabama Senate candidate Roy Moore amid allegations he molested underage girls and Donald Trump despite the sexual misconduct accusations against him.

“This is the Republican Party,” DCCC spokeswoman Sabrina Singh said in a statement. “Democrats will refuse to stand by while the Republican Party denigrates women.

“We will continue to march side by side with women all across this country because we believe that women must be empowered and respected.”

Wynn played a major role in the revitalization of the Las Vegas Strip in the 1990s. It was his company that built the Golden Nugget, Bellagio and Mirage Resorts in the heart of the town.

The Wall Street Journal stated that none of the alleged victims reached out to it. The newspaper said it sought out more than 150 people who had worked for Wynn, many of whom did not want to go on record.

The newspaper reported that Wynn’s actions were well known enough that employees would sometimes enter fake appointments to help other female workers avoid him. In some cases, it said, female salon employees would hide in back rooms if they knew Wynn was on his way to the casino.

Wynn Resorts said there had never been a complaint made about Wynn to the company’s independent hotline for anti-harassment.