Winston Churchill’s grandson has called Boris Johnson’s use of claims that the “part-Kenyan” US President has an “ancestral dislike" of the British empire “deplorable and completely idiotic”.

The Mayor of London alleged that a bust of Churchill had been “banished” from Barack Obama’s office in an attack on his intervention in the EU referendum debate.

“Some said it was a snub to Britain,” Mr Johnson wrote in The Sun.

Boris on US foreign policy

“Some said it was a symbol of the part-Kenyan President’s ancestral dislike of the British empire – of which Churchill had been such a fervent defender.”

Sir Nicholas Soames, the wartime Prime Minister’s grandson, called the claims a “completely desperate” move by Mr Johnson as he fronts the Vote Leave campaign.

"I'm mad enough to think it was probably written by some little twerp who works for Boris,” he told LBC radio.

"I can't believe that Boris would really have done something so stupid.

"But whatever it is, it bears his name and it's deeply offensive."

A bust of Churchill lent to George Bush during his Presidency was removed from the Oval Office in 2009 but a second bust of Churchill remains elsewhere in the White House (AFP/Getty Images)

Sir Nicholas, the Conservative MP for Mid Sussex, said one bust of Churchill was lent to George Bush during his time as President but ended its lease before his successor took office in 2009.

Another head of Churchill remains in apartments used by the Obama family, he added.

“Boris needs to grow up, because it is not obligatory for any of us to have a head of Winston Churchill in our bedroom,” Sir Nicholas said.

“Why should the President of the United States have a head of my grandfather in his room? It’s very nice that he did but I don’t regard it as being a terrible crime.”

He added that he was “not in the least bit offended” by the US President’s support for David Cameron’s position on the EU, and said Churchill would not have been concerned either.

Winston Churchill: Life in pictures Show all 30 1 /30 Winston Churchill: Life in pictures Winston Churchill: Life in pictures Winston Churchill Winston Churchill leaving London for his country home, Chartwell in Kent in 1964 Winston Churchill: Life in pictures Winston Churchill Sir Winston Churchill with his daughter Mary and son-in-law Christopher Soames (right) in 1964 PA Winston Churchill: Life in pictures Winston Churchill (Seated left to right) Air Chief Marshal Sir Charles Portal; Field Marshal Sir Alan Brooke, Winston Churchill; Admiral Sir Andrew Cunningham, (standing left to right) the Secretary to the Chiefs of Staffs Committee, Major General L C Hollis; and the Chief of Staff to the Minister of Defence, General Sir Hastings Ismay at an unknown location Winston Churchill: Life in pictures Winston Churchill Winston Churchill flashes the V-sign on 19 June 1963 AFP PHOTO Winston Churchill: Life in pictures Winston Churchill Winston Churchill feeds the deer in Richmond Park, accompanied by his private secretary Anthony Montague Brown and personal detective Edmund Murray on 25 March 1963 Winston Churchill: Life in pictures Winston Churchill Winston and Lady Churchill leaving their Hyde Park Gate home for an Ascot race meeting on 16 June 1961 Winston Churchill: Life in pictures Winston Churchill Jacob Epstein with Winston Churchill in 1958. The pair lived on the same London street Evening Standard/Getty Images Winston Churchill: Life in pictures Winston Churchill Prime Minister Winston Churchill kisses Queen Elizabeth II's hand as she leaves 10 Downing Street in London, after a dinner on 4 April 1955 Getty Images Winston Churchill: Life in pictures Winston Churchill Winston Churchill at the christening of his granddaughter, Charlotte Soames at Westerham Parish Church, Kent on 6 November 1954. Left to right: godparents Fitzroy MacLean and Diana Churchill, Sir Winston Churchill, Lady Clementine Churchill, Christopher Soames and his wife Mary Churchill. The children are Nicholas, Jeremy and Emma Soames with his grandson Nicholas Soames Winston Churchill: Life in pictures Winston Churchill French President Paul Ramadier awards the medaille Militaire to former British prime minister Winston Churchill on 12 May 1947 Winston Churchill: Life in pictures Winston Churchill Winston Churchill outside the German Reichstag during a tour of the ruined city of Berlin on 16 July 1945 PA Winston Churchill: Life in pictures Winston Churchill The prime minister of the wartime Coalition government Sir Winston Leonard Spencer Churchill during a speech 0n 2 July 1945. The July 1945 general election resulted in a resounding victory for the Labour Party Winston Churchill: Life in pictures Winston Churchill British Prime Minister Winston Churchill (L) walking with General Bernard Law Montgomery near the Rhine river in Germany during an advance by Allied troops on 23 March 1945 Winston Churchill: Life in pictures Winston Churchill Marshal Joseph Stalin and Winston Churchill together at the Livedia Palace in Yalta, where they were both present for the conference on 7 February 1945 Winston Churchill: Life in pictures Winston Churchill Winston Churchill with his daughter Mary and General Sir Frederick Pile (GOC Anti-Aircraft Command) watch anti-aircraft guns in action against V1 flying bombs on 30 June 1944 Winston Churchill: Life in pictures Winston Churchill Winston Churchill and General Sir Bernard Montgomery with his dog in 1944 Winston Churchill: Life in pictures Winston Churchill Prime Minister Winston Churchill Prime US President Franklin D. Roosevelt seated in the garden of the villa in Morocco where they met for a war conference surrounded by British and American war correspondants, on 23 January 1943 PA Winston Churchill: Life in pictures Winston Churchill Winston Churchill and his wife, Clementine, on board a naval auxiliary patrol vessel during a visit to the London docks on 25 September 1940 Winston Churchill: Life in pictures Winston Churchill First Lord of the Admiralty, Winston Churchill strolls in the grounds of his country home, Chartwell Manor on 31 October 1939 Topical Press Agency/Getty Images Winston Churchill: Life in pictures Winston Churchill Winston Churchill, recently appointed Hon Air Commodore to 615 Auxiliary Air Force Squadron, climbing out of a Gloster Gauntlet II aircraft during a visit to the Squadron at Kenley, Surrey on 16 April 1939 Winston Churchill: Life in pictures Winston Churchill Winston Churchill balancing a top hat on his walking stick watched by his daughter Mary, outside the Mansion House in London Winston Churchill: Life in pictures Winston Churchill British statesman Winston Churchill attends the Anglo-Irish Conference in Downing Street on 11 October 1921 Winston Churchill: Life in pictures Winston Churchill The platform party is attentive to Winston Churchill as he delivers his address opening a new YMCA hostel for munitions workers at Enfield, Middlesex, on 20 September, 1915 Winston Churchill: Life in pictures Winston Churchill Winston Churchill won his first parliamentary seat in 1899 Getty Images Winston Churchill: Life in pictures Winston Churchill 2nd Lieutenant Winston Churchill of the 4th Queen's Own Hussars in 1895 Winston Churchill: Life in pictures Winston Churchill Winston Churchill dressed in the uniform of Harrow School Rifle Corps Save Photo Winston Churchill: Life in pictures Winston Churchill Winston Churchill between the ages of 13 and 17 at the time he attended the Harrow School Save Photo Winston Churchill: Life in pictures Winston Churchill Winston Churchill in his school years Save Photo Winston Churchill: Life in pictures Winston Churchill The former Jennie Jerome, Lady Randolph Churchill, born in New York, with her sons John (left) and Winston, in 1885 Time Life/Getty Winston Churchill: Life in pictures Winston Churchill Winston Churchill as a young boy, aged 7, in Dublin, Ireland

Sir Nicholas, who is staunchly pro-EU, said he launched his scathing attack on Mr Johnson “with regret”, adding: “Boris has been a friend of mine for many, many years and I’m fond of him, but this is business.”

The row dominated the first day of Mr Obama’s visit to the UK on Friday, when he held talks with the Prime Minister before meeting the Queen and other members of the Royal Family.

When questioned on Mr Johnson’s article, the President clarified that there had once been two busts of Churchill in the White House and that the statue formerly kept in the Oval Office had been replaced by one of Martin Luther King.

“I love Winston Churchill, I love the guy,” Mr Obama said, describing seeing the remaining head “every day”.