The firm, Davidson Ryan Dore, is distributing recordings and pictures, smuggled out from Ms Karimova's house in the capital Tashkent, where she says she is being held.
New pictures earlier this week showed Ms Karimova apparently being manhandled by security guards.
The images are a far cry from the glamorous photographs depicting President Karimov's eldest daughter in her previous persona as a pop diva, philanthropist and fashion designer.
Even a year ago Ms Karimova was regarded as one of the most influential and powerful people within the country's elite and a potential successor to her father.
But after a dramatic and public falling out with her family, her privileges and assets have been stripped away. Earlier this month the authorities announced she was under criminal investigation.
The latest pictures show Ms Karimova in the presence of camouflaged guards. In two of the images guards are seen handling her directly as she appears to be arguing.
Last month secret recordings were circulated in which Ms Karimova gave details of her situation in her own voice, saying she and her teenage daughter were being treated "worse than dogs" and needed urgent medical help.
One of the founders of Davidson, Ryan, Dore, the firm distributing the materials, has taken on the function of spokesperson for Ms Karimova.
"We as a firm were appointed three months ago by the friends and family of Gulnara internationally," Locksley Ryan told BBC Uzbek. He did not confirm whether Ms Karimova's son Islam, who studies in London, was involved in appointing the firm.
Mr Ryan said that the firm had several ways of making contact with Ms Karimova but that it was extremely difficult.
The latest pictures, he said, were simply showing how she was under guard 24 hours a day, seven days a week.
"It's in complete isolation. The only people that she can talk to are her daughter who is trapped there with her and obviously the guards."
Mr Ryan said there was evidence that Ms Karimova was even denied food.
In the audio recordings which appeared last month, Ms Karimova said her situation had deteriorated greatly.
"The territory of the house is basically surrounded now by hundreds of cameras and special equipment which is blocking any means of communication. So it's tremendous pressure and stress on me and my daughter. We need medical help urgently," Karimova says in one of the recordings.
Locksley Ryan says that after the recordings were made public, all staff at the house were Ms Karimova is being held were moved.
"Once those were forwarded to various outlets, suddenly all of the personnel from the house were removed and sent everywhere."
In a statement on a new website called Free Gulnara Now, Mr Ryan says that the president's daughter was directly appealing to the international community "that her fate be determined by the independent courts and not by individuals battling for political gain".
Ms Karimova has been linked to several investigations in Europe, including a corruption investigation in Switzerland where bank accounts linked to her have been frozen.
Ten days ago the Uzbek prosecutor's office announced that Ms Karimova was being investigated in Uzbekistan over alleged links to a criminal group.
"If there are claims that she has done something wrong then let her face those claims. Let her go to Switzerland and understand the accusations made to her and let a court decide," Mr Ryan told the BBC.
He dismissed the Uzbek accusations as politically motivated.
"Is it just a coincidence that at a time that the election campaign starts suddenly the prosecutor deems to start to investigate her?"
Ms Karimova was long considered to be a potential successor to her father - elections are due next year.
Davidson Ryan Dore's strategy appears to be to try to get Ms Karimova out of the country to answer allegations in a European court.
Mr Ryan says that the sentencing of several of Ms Karimova's associates shows that the Uzbek legal system is unlikely to deliver justice.
"It is unknown to me how someone can get investigated, prosecuted and disappear into a military court and then be sentenced with no access to any form of public scrutiny, maybe not even have lawyers. I can't see how that can be just."
Human rights groups have long criticised what they say is the country's abysmal human rights record.
But observers say that Ms Karimova's own fall from grace and subsequent detention is hardly comparable to the fate of those suffering torture and abuse in Uzbek prisons.
A London-based public relations firm is acting on behalf of Gulnara Karimova, the once powerful daughter of Uzbekistan's authoritarian president who has been under house arrest for months.