Britain's High Court refused a request from Qatar's Doha Bank to exclude evidence of alleged witness intimidation from a terrorism financing case.
Four Syrian refugees lodged a case for damages at London's High Court against Doha Bank, as well as Moutaz and Ramez Al Khayyat.
The refugees alleged the brothers used Doha Bank accounts to channel money to the Al Nusra Front, an Al Qaeda affiliate.
The Syrians said they suffered "severe physical and psychiatric injuries" at the hands of the terrorist group, and that Qatar threatened, intimidated and attempted to bribe them in a bid to dissuade them from pressing ahead with their case.
A hearing is scheduled for October to determine whether the trial will be held in the UK or Qatar.
Doha Bank's lawyers applied for the allegations of intimidation to be dropped from proceedings.
But Justice Martin Chamberlain ruled that the judge hearing the case should hear the allegations.
"Evidence which relates not to the underlying allegations but to the alleged interference in these proceedings by the defendants or agents of the State of Qatar should be before the judge, because this evidence is directly relevant to the suitability of the State of Qatar as a forum," he said.
"I will permit all of the claimant's evidence which relates to alleged attempts by the defendants or others on behalf of the State of Qatar to interfere with the course of justice in these proceedings.
"At present the claimants have not identified any parts of their evidence going to these issues beyond those referred to in Doha Bank's skeleton argument, but I will give a further opportunity to the claimants to do so, and for Doha Bank to respond, in the light of the approach I have outlined in this judgment."
Last year, a report was made to London's Metropolitan Police accusing Qatar of perverting the course of justice and of witness intimidation.
The court previously heard that people connected with the case had their cars bugged, were threatened in their homes and were offered bribes to reveal the names of the claimants, who were granted anonymity by the court.
Eight refugees had originally filed claims but four withdrew their cases last year claiming they were in “fear of their lives”.
An application by the claimant's legal team to cross-examine the Al Khayyat brothers at the October hearing was refused.
Mr Chamberlain said it would be inappropriate and would turn the hearing into a "mini trial".
A spokesman for the Al Khayyat brothers told The National they denied the "bizarre and baseless allegations".