Donald Trump's daughter-in-law and senior adviser, Lara Trump, has criticised a joke made by Johnny Depp about assassinating the US President – calling it "really sad" and "incredibly disappointing".

The US actor was at Glastonbury Festival on Thursday (22 June) presenting a screening of his 2004 film The Libertine, when he asked the crowd: "Can we bring Trump in?"

When festival goers responded with jeers, Depp continued: "No, no, no. You misunderstand completely ... When was the last time an actor assassinated a president? I want to clarify: I'm not an actor. I lie for a living. However, it's been a while. Maybe it's about time."

The crowd responded with laughter, cheers and applause.

Depp later apologised for his remarks, calling it a "bad joke" that was "in poor taste".

"It did not come out as intended, and I intended no malice. I was only trying to amuse, not to harm anyone," he said in a statement on Friday.

But in an interview with Fox News, Lara Trump said the actor's joke was part of a "bigger problem" where threats of violence against the US President had become "normalised".

"The people in this country are sick and tired of this sort of thing. They don't think it's cute, they don't think it's funny – Johnny Depp is not doing himself any favours with fans of his by doing things like this.

"It really does speak to a bigger problem which is that this sort of thing has become normalised. We see what happened with Shakespeare in the Park, we see Kathy Griffin, we see Late Night hosts [and] Madonna going to blow up the White House. This is just out of control and it's really, really sad.

"As a family member and as an American, it's incredibly disappointing."

The White House also slammed Depp's comments, saying on Friday: "President Trump has condemned violence in all forms and it's sad that others like Johnny Depp have not followed his lead.

"I hope that some of Mr. Depp's colleagues will speak out against this type of rhetoric as strongly as they would if his comments were directed to a Democrat elected official."

Lara, who married Eric Trump in 2014, says her father-in-law is also being unfairly singled out and attacked by Democrats.

"Let's be very clear: this has never happened in this capacity to any other president," she said.

"It's happening to Donald Trump because he is Donald Trump. Because their candidate failed, because they have nothing else to say. They have no platform. They have no real leader. They have no real message.

"So the only real thing they can do is pile on the president, and unfortunately, it is to the detriment of the country. And instead of trying to be proactive and help pass legislation that might be beneficial to the people of this country, instead it's just all anti-Trump."

Johnny Depp
Johnny Depp introduces a screening of The Libertine film at the Cineramageddon cinema on day 1 of the Glastonbury Festival 2017 Ian Gavan/Getty Images