Koprivica even claims that Joseph Stalin may have known about romance

She claims Churchill tried to cover up romance by altering mother's diary

Winston Churchill was the illegitimate son of the King of Serbia, a new book claims.

Author Dragoslava Koprivica claims the former British Prime Minister's mother had a secret relationship with Milan Obrenovic before he went on to rule the Balkan state.

She also alleges that Churchill tried to cover up the romance by altering his mother's diaries.

In her book King Milan and Lady Churchill, Koprivica, 44, says she spent years studying archives across Europe, gathering information on Jeanette Jerome, who became Lady Randolph Churchill when she married Churchill's father Randolph in 1874.

Winston Churchill (left) was the lovechild of Milan Obrenovic (right) before he become the King of Serbia, according to a book by Dragoslava Koprivica who says she spent years studying records across Europe

Koprivica claims her sources included the diary of one of the Lady Churchill's sisters which reportedly described her love for Milan Obrenovic.

During her research, Koprivica also found letters from the Obrenovic family that reportedly made it clear they knew about this love.

She says Milan Obrenovic and Lady Churchill met in Paris in 1867 while they were studying and that she left diaries which Churchill allegedly altered to hide the romance.

She said: 'After his mother's death Churchill took her diary and removed from it all the pages where her love relationship with Obrenovic was described.

'There are many gaps in the biographies about Churchill's family about the time when Lady Churchill was married and conceived.

Koprivica alleges that Churchill removed pages from the diary of his mother Jeanette Jerome (left), who became Lady Randolph Churchill when she married Churchill's father Randolph (right)

'There is also clear evidence that Churchill was interfering with his and his mother biographies and in the relevant years removed everything that he didn't like.'

According to Koprivica, the memoirs, diaries and letters show that her son was in fact the child of the Serbian king Milan Obrenovic (1854-1901), who was notoriously unfaithful to his wife

Presenting her book in the north Serbian town of Gornji Milanovac, she said: 'I used hundreds of books and details from different archives to complete the book in three years.'

She added that Joseph Stalin probably knew of the relationship.

Lady Churchill pictured with her sons Winston (right) and John circa 1885

She said one of the compelling pieces of evidence was at the Yalta Conference in 1945 when Churchill met Stalin and the US president Roosevelt to decide upon the fate of post-war Europe.

Churchill was apparently strongly against the idea of a monarchy prevailing in the Kingdom of Yugoslavia at the Yalta Conference.

Koprivica used some records by Stalin in which he wrote that both him and Roosevelt were surprised by Churchill's support for the Communists of Yugoslavia.