Bucks County portrait artist Nelson Shanks is recognised far and wide for painting famous personalities, including the late Princess Diana, Pope John Paul II, Margaret Thatcher, and Bill Clinton.

And while many revere his talent, the Clintons have good reason to hate the one he did on the former US President. And Shanks recently told Philly.com's news writer Stephanie Farr why.

"If you look at the left-hand side of it there's a mantel in the Oval Office and I put a shadow coming into the painting and it does two things," he said during the interview. "It actually literally represents a shadow from a blue dress that I had on a mannequin, that I had there while I was painting it, but not when he was there. It is also a bit of a metaphor in that it represents a shadow on the office he held, or on him."

The blue dress, of course, was owned by Monica Lewinsky - a White House intern who also became Clinton's paramour. Their "inappropriate relationship" eventually led to Clinton's impeachment and he was forced to step down from his office.

It is for that reason that the Clintons hate the painting and want it removed from the National Portrait Gallery, according to the painter. Shanks said that the gallery is under a lot of pressure to remove it, but a spokesperson from the gallery denied his claims.

Shanks added that Clinton was also the most difficult figure he had to paint, and it is because of the political figure's complex layers.

"Clinton was hard. I'll tell you why. The reality is he's probably the most famous liar of all time. He and his administration did some very good things, of course, but I could never get this Monica thing completely out of my mind and it is subtly incorporated in the painting," he said.

Shanks' desire to see through a person's facade is one of the reasons why many of his subjects apparently feel very uncomfortable while he is painting them. "There are plenty of them I've made nervous. Especially Clinton. Oh, he was petrified," he recalled.

On the other hand, there were others who appreciated and lauded his insight. "When they were unveiling the portrait of Margaret Thatcher, Margaret said 'Nelson is not only a painter, he's a philosopher," shared Shanks. "And that just did it for me. That really blew me away."