Alex Haley, author of "Roots," said yesterday he is prepared to defend his best-selling account of his ancestry against charges by a British Journalist that the facts do not support it.

Haley, who left New York yesterday for London, said just before his departure that he hoped he would have an apportunity to meet his critic, Mark Ottaway of the Sunday Times, "head on."

"Here's a guy who spent perhaps two weeks putting his story together, and I spent 12 years on my book - nine years of research and three years of writing."

"I will be most happy to meet with the press in London, preferably in the presence of Mr. Ottaway," Haley said from Kennedy Airport.

Haley said he and Ottaway had a long talk before the article was written.

"Ottaway makes substantial misrepresentations of my statements to him in the course of our conversation, and he makes accusations that are totally unfounded in terms of what he says I said in the book," Haley said.

Haley's flight to London also coincided with the showing on British television of the six-part film adaptation of "Roots" that attracted the biggest viewing audience in American broadcast history.

In "Roots," Haley describes tracing his family back to the Gambian village of Juffure and the abduction there in 1767 of his ancestor, Kunta Kinte, by British slavers.

In his 5,000-word copyrighted article in The Times, Ottaway made these points:

The real Juffure of 1767 differed fundamentally from the ancestral village of Haley's book. Far from being untouched by white civilization, it was in fact a white trading post.

Insofar as the inhabitants of Juffure were involved in slave trading it was not as victims but as collaborators, capturing slaves from farther up river. It is highly unlikely that a resident of Juffure could have been captured by slavers in 1767.

Haley chose that year not because it accorded with information he was given in Gambia, but because it was the only year that could possible fit in with his researches in the United States.

The vital link in Haley's claim to have traced his ancestry to Kunta Kinte was provided by a man of notorious unreliabity who knew in advance what Haley wanted to hear and who subsequently gave a totally different version of the tale.

The Kunta Kinte who apparently once disappeared from Juffure must have done so later than 1767, and capture by slavers is the least likely of all possible explanations. No one knows what happened to him.

Haley conceded yesterday the certainty of probability of all of those points to Ottaway and conceded he may have been misled during his historical researches in Gambia, The Times said. He said he had considered calling the African section of his book a "historical novel" but in the end decided to believe what he had been told.

When he went to Gambia 10 years ago, a seminar of tribal experts organized for him said that as there was no written Gambian history he would have to consult a griot or member of a heredity caste who recorded the feats and family trees of those they serve. In a moving part of the book Haley describes how he "sat as if carved of stone" in the village of Juffure listening to the griot.

Haley wrote that there was no way this African could have known the boyhood stories he had heard in Tennessee.

In fact, says Ottaway, the seminar was told the whole story and set out to find a griot who had a story that might fit.

It was only when the search was widened outside the territory of the Kinte family was Kebba Fofana found. It was he who gave Haley the account of Kinte history. He remembered a Kinte who dissapeared while chopping wood and provided him with a first name, Kunta.

Kebba Fofana died nine months ago, so his story can no longer be checked. But according to Ottaway he was not a griot and indeed was something of a playboy who had not enough Koranic scholarship or moral fiber to follow his father as an imman.