Descendants, who have long believed Jefferson had a relationship with his slave Sally Hemings, welcomed the statement from the Thomas Jefferson Memorial Foundation.

The foundation made its statement after examining a DNA study, which found genetic links between descendants of the former president and those of the slave.

Lucian Truscott IV - a member of the Monticello Association made up of Jefferson's descendants - believes the Hemings' descendants should be treated as true relatives.

He said: "[The statement] is like the Civil Rights Act for the Hemings family.

"It's what I believe and it's what the Hemings have known for 200 years."

The Hemings family has always believed it was related to the third president of the United States - largely due to stories passed from generation to generation.

Shay Banks-Young, a descendant of Sally Hemings, said: "It's about time that someone is validating what oral history has confirmed for years."

The issue remains controversial as Thomas Jefferson is an American icon. He was the one of the authors of the Declaration of Independence.

Such is the reverence for his place in history, that many of his white descendants categorically rejected the DNA study when it was first published in 1998, which said there was strong evidence that he had fathered as many as five children with his slave.

But the chairwoman of the memorial foundation's research committee, Dianne Swann-Wright, noted that President Jefferson freed all of Sally Hemings' children when they were adults - a highly unusual move for the time.

According to the committee's report, Jefferson gave freedom to no other slave family.

"I think that speaks for itself," Ms Swann-Wright said.

Denies membership

The foundation said that while it could not be established with absolute certainty, there was a strong likelihood that he had fathered at least one and possibly all of Sally Hemings's children.

Foundation president Daniel Jordan said: "Although paternity cannot be established with absolute certainty, our evaluation of the best evidence available suggests the strong likelihood that Thomas Jefferson and Sally Hemings had a relationship over time that led to the birth of one, and perhaps all, of the known children of Sally Hemings."

The Monticello Association which includes most of Thomas Jefferson's direct descendents continues to deny membership to Sally Hemings's family.

But the statement by the trustees of Jefferson's estate will increase the pressure on the association's members to acknowledge that they do have black relatives.

The association is planning to release its own report on Jefferson descendants later this year.