The husband of key White House adviser Kellyanne Conway wrote Thursday night that the report of special counsel Robert Mueller provides sufficient grounds to impeach President Trump.

In an op-ed in The Washington Post published online, lawyer George Conway wrote under the headline “Trump is a cancer on the presidency. Congress should remove him” that, contrary to claims by his wife and by Mr. Trump, the “damning” report did not exonerate him.

“White House counsel John Dean famously told (President Richard) Nixon that there was a cancer within the presidency and that it was growing,” Mr. Conway wrote. “What the Mueller report disturbingly shows, with crystal clarity, is that today there is a cancer in the presidency: President Donald J. Trump. Congress now bears the solemn constitutional duty to excise that cancer without delay.”

Mr. Conway said the fact Mr. Mueller refused to recommend criminal charges, and the Justice Department declined to bring any, is an irrelevant side issue.

“Mueller couldn’t say, with any ‘confidence,’ that the president of the United States is not a criminal. He said, stunningly, that ‘if we had confidence after a thorough investigation of the facts that the President clearly did not commit obstruction of justice, we would so state.’ Mueller did not so state. That’s especially damning because the ultimate issue shouldn’t be — and isn’t — whether the president committed a criminal act.

“As I wrote not long ago, Americans should expect far more than merely that their president not be provably a criminal. In fact, the Constitution demands it,” he wrote in the Post op-ed.

Mr. Conway has repeatedly attacked Mr. Trump, despite Mrs. Conway’s job in the White House and her role in steering the 2016 Trump campaign to a stunning victory. The president himself has even attacked Mr. Conway back, saying he is embarrassing his wife.