A TV screenshot shows actress Mia Farrow testifying at the war crimes trial of former Liberian president Charles Taylor at the UN Special Court for Sierra Leone in The Hague on Monday. (Reuters TV)

Naomi Campbell's former business agent told a war-crimes court Monday the fashion model flirted with former Liberian president Charles Taylor at a 1997 dinner and he arranged to send her a gift of uncut diamonds.

Earlier actress Mia Farrow testified that Campbell told her she had been sent a "huge diamond" by Taylor, directly contradicting Campbell.

The prosecution called Farrow and Campbell's former agent, Carole White, to testify about a gift of uncut diamonds the former Liberian president allegedly gave the model at a September 1997 party hosted by Nelson Mandela.

But under cross examination, defence lawyers strongly challenged the testimony of both Farrow and White.

"You have a very powerful motive for lying," Courtenay Griffiths said, noting that White is currently suing Campbell for millions of dollars over an alleged breach of contract.

White's testimony contradicts the British model's statements at the Sierra Leone Special Tribunal.

Campbell downplayed her contact with Taylor, saying she received an unexpected gift of "dirty looking" pebbles the night after the dinner.

She told judges Friday she did not initially realize they were diamonds or who sent them.

Prosecutors say White's testimony Monday could help prove Taylor traded guns for uncut diamonds with rebels in neighbouring Sierra Leone during its 1992-2002 civil war.

Campbell told the court in The Hague on Friday that she was given several small stones by unknown men during the night. She said she hadn't known they were diamonds and didn't know who had sent them.

The prosecution claims Taylor traded guns to rebels in neighbouring Sierra Leone in exchange for uncut diamonds during the country's 1992-2002 civil war, which left more than 100,000 people dead. The stones are known as "blood diamonds" because they are used to finance conflicts.

A huge diamond

Farrow testified that Campbell told other guests over breakfast she had received a diamond from Taylor.

"She said that in the night she had been awakened, some men were knocking at the door, and they had been sent by Charles Taylor, and they had given her a huge diamond," Farrow said.

But under lengthy cross examination, Farrow, 65, conceded she had never seen the diamond or diamonds herself.

"I think I would have remembered diamonds in the plural," Farrow said, calling it "sort of an unforgettable moment."

Taylor faces 11 charges at the Special Tribunal for Sierra Leone, including murder, rape, sexual enslavement and recruiting child soldiers. Prosecutors allege he armed and commanded Sierra Leone rebels who murdered and mutilated thousands of civilians.

Taylor denies all the charges.

In court, Judge Julia Sebutinde asked Farrow whether it was possible she might have seen the 2006 movie Blood Diamond and been influenced by its plot, which centres on a single large diamond.

"Your honour, I know she didn't say a few, certainly not 'stones'." Farrow said. "She may not have used the word 'huge', but it wasn't several diamonds, and it certainly wasn't stones because ... why would she give stones to Nelson Mandela's charity?"

Outside the courtroom, Taylor defence lawyer Courtenay Griffiths said Farrow sees herself as a "Mother Teresa" of Africa and pointed to her activism on behalf of victims of conflict, especially those in Sudan's troubled Darfur region.

In the courtroom, defence lawyers showed that Farrow had edited portions of a newspaper article posted on her website last week to remove words favourable to Taylor. On the stand, she said Sudan's president, Omar al-Bashir, is "guilty" of war crimes even though he has been charged with war crimes but not yet tried.

The defence lawyer said Farrow's testimony is not credible given that it contradicts the known number of diamonds given to Campbell and is based on events from a single breakfast 13 years ago.

"Either Mia Farrow is lying, for her own reasons, or, alternatively, she is totally mistaken," Griffiths said.