Former first dog Barney, George W. Bush's black Scottish terrier has died at the age of 12 after losing a battle to lymphoma, the ex-president said.

A fixture throughout the presidential grounds during Bush's 2001-2009 term, Barney had starred in "Barney Cam" holiday specials in which he gave a dog's eye view of even the most cold-faced White House staff, alongside his companion Miss Beazley, another black Scottish terrier.

Barney even had his own page on the White House website.

Coinciding with the pooch's death, Bush also unveiled to the public for the first time artwork of his own making.

The 43rd president has taken up painting since retiring from office, and he posted an oil painting rendition of his beloved dog on Facebook. It was signed simply "43."

"Barney and I enjoyed the outdoors. He loved to accompany me when I fished for bass at the ranch. He was a fierce armadillo hunter. At Camp David, his favorite activity was chasing golf balls on the chipping green," Bush said in a statement.

"Barney guarded the South Lawn entrance of the White House as if he were a Secret Service agent. He wandered the halls of the West Wing looking for treats from his many friends. He starred in Barney Cam and gave the American people Christmas tours of the White House.

"Barney greeted queens, heads of state and prime ministers. He was always polite and never jumped in their laps," Bush added.

"Barney was by my side during our eight years in the White House. He never discussed politics and was always a faithful friend. Laura and I will miss our pal."

Along with the painting, Bush also released dozens of pictures of his dog on Facebook.

All 20th century US presidents with the exception of Woodrow Wilson have had a dog in the White House. President Harry Truman (1945-1953) even reportedly said, "If you want a friend in Washington, get a dog."