Donald Trump must be removed from office as he is “not well at all mentally”, a former White House ethics chief has said.

Richard Painter, who served as George W Bush’s ethics lawyer between 2005 and 2007, told cable network Msnbc Mr Trump’s national emergency declaration over illegal immigration was “clearly illegal” and the product of the president’s state of mind.

“The president is not well at all mentally. I think he’s an extreme narcissist. He has been denied what he wants, his wall, and he is having a hissy fit,” said Mr Painter.

“He is out of control, and he will not take no for an answer from Congress. And he’s going do this. He is going to insist on doing it, he is going to tear the country apart. It’s unconstitutional, it’s illegal.

“He is going to do enormous damage to the Republican Party which is going to split right down the middle over this, and we really need to keep in mind that this is because the president is not well.”

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Mr Painter, vice-chair of Citizens for Responsibility and Ethics in Washington, which filed a lawsuit against the declaration hours after its announcement, cited Mr Trump’s belief of Vladimir Putin over US intelligence officials as evidence of his irrationality.

“He is not capable of doing the job. He does need to be removed under the 25th amendment, but he stocked his cabinet with people who are unwilling to do that, and Congress is apparently unwilling to even try to remove him through impeachment,” Mr Painter said.

On Monday, a coalition of 16 US states, led by California, sued the Trump administration over last week’s emergency declaration, which gives Mr Trump powers to allocate federal funds for segments of a barrier across the US-Mexico border.

The move came after Congress refused to grant Mr Trump the $5.7bn (£4.4bn) he initially demanded in wall funding, a row which led to a record 35-day government shutdown late last year.

“Today, on Presidents Day, we take President Trump to court to block his misuse of presidential power,” California attorney general Xavier Becerra said in a statement.

“We are suing President Trump to stop him from unilaterally robbing taxpayer funds lawfully set aside by Congress for the people of our states. For most of us, the Office of the Presidency is not a place for theatre.”