Oliver Cromwell should be exonerated for his “war crimes” and the Irish nation issue a posthumous apology for “blackening his name,” according to the author of a controversial new book.

Tom Reilly’s book Cromwell Was Framed challenges historians and academics who claim the former Huntingdon MP and military leader ordered the killing of thousands of unarmed Irish men, women and children at the Irish towns of Drogheda and Wexford in 1649.

Accounts of the time claim Cromwell’s army invaded and attacked the Royalist forces and, once the troops were defeated, he slaughtered the civilian survivors.

Reilly, who lives in Drogheda, County Louth, says two individuals are responsible for pedalling lies and misinformation about events on the battlefields.

“I looked at all the available sources of information in chronological order and realised there were very few eyewitness accounts of civilian deaths and those that do exist are attributed to two individuals. These two people, who were Royalists, had access to a printing press, which was not common at the time, and so they had the means to pedal lies,” he said.

“In 1649, Cromwell issued a proclamation stating that he did not kill civilians, which he repeated 10 times, and he did, in fact, issue a battle order that ‘common people were exempt’ from killing.”

Reilly does name the two individuals in his book and includes contemporary documentation to support his findings. He says he is aware that feelings about Cromwell and the massacre, which led to famine and an outbreak of bubonic plague, in his home town of Drogheda still run high.

“For me it is important that people know what really happened. We need to stop teaching our children lies,” he said.

“The reporting of these two battles amounts to the worst form of tabloid journalism and is based on unsubstantiated myth.”

There was an outcry in 2000 when the British Museum lent Cromwell’s death mask to the Drogheda Heritage Centre as part of an exhibition. The walls of the heritage centre were daubed in tomato sauce to represent the blood of Cromwell’s victims. Local councillor Frank Godfrey said at the time: “The people of Drogheda suffered greatly. Men, women and children were massacred, and we don’t forget.”

John Goldsmith, curator of the Cromwell Museum, said he had never taken sides on the issue of Cromwell in Ireland and was looking forward to reading Reilly’s new book.

“This is Tom’s second book and he has previously made a good case to say that Cromwell has been badly treated by history. There doesn’t seem to be any conclusive proof either way on Cromwell and the Ireland issue. The leading academics disagree on the subject, so hopefully Tom’s new book will add something different to the debate.”

Mr Goldsmith said the museum would be stocking copies of the book.