Donald Trump launched a 1,300-word social media rant against the late-night US TV host Bill Maher on Sunday evening, calling him a “TOTAL LOSER” in a fresh assault on the media.

“Let’s talk about this COMPLETE AND TOTAL LOSER, Bill Maher,” the US president wrote. “He’s got a Low Rated Show on equally Low Rated HBO, which was once, long ago, a Network of Quality and Excitement – But that’s all gone.”

Trump’s lengthy and detailed post about Maher came after the host interviewed Karoline Leavitt, the former White House press secretary, on his program Real Time with Bill Maher.

Maher asked Leavitt about Trump’s “lame duck” presidency and whether the president would act on “vengeance” if Republicans largely lose to Democrats in next week’s midterms.

“I worry that if this election goes as badly as it looks like it’s going to go for him and the Republicans, we’re going to have a guy who doesn’t have as much power as he did … and we know he likes vengeance,” Maher told Leavitt.

But Leavitt remained steadfast in her support for Trump and expressed confidence that Republicans could still outperform expectations.

Trump called Maher a “coward who is afraid to tell the truth about how well our Country is running”, claiming that Maher praised him behind the scenes but on television insults him with jokes.

“Also, turn your Laugh Machine off, it’s a joke when they laugh uncontrollably, even when you say nothing funny, and I’m going to have the Republicans not cover you anymore, because they try to talk about you as a guy who is transformative,” Trump wrote.

Trump has previously insulted late-night hosts and comedians on his platform and taken personal offense at those who make him the punchline. Earlier this year, Trump called for Jimmy Kimmel’s show to be terminated after the ABC late-night host joked about Melania Trump. Last year, the US president also called for Seth Meyers to be fired.

But Trump’s lengthy attack on Maher is notable, coming just about a week until the US midterm elections, where Republicans are trying to fend off challenges from Democratic opponents.

The US president chose to launch a tirade against Maher as public polling shows Americans are growing increasingly unhappy with Trump’s handling of the US economy, cost of living and war with Iran.

But Trump chose to dispute several specific talking points Maher made on his show, including the host’s comments about the justice department’s efforts to target ballots they claim were cast by noncitizens in California, rumors that Trump is turning the White House press briefing room into a swimming pool and Trump’s endorsement of Republican candidates in the upcoming midterms.

Maher, who has been described as a moderate liberal, has dined with Trump on two occasions during the US president’s second administration. Maher has shared his experience with Trump on his HBO show.

Among other insults Trump launched at Maher, he accused the host of drinking a lot of alcohol when they dined together, being a “POTHEAD”, not being nice and catering to a base of viewers who “don’t like working”.