She had been given power of attorney over the cash in late February from her father, double agent Sergei Skripal, poisoned by nerve agent Novichok alongside her on March 4 in Salisbury. The pair were found slumped on a bench in an outdoor shopping complex after the attack with no visible injuries, according to police.
"We have not identified the precise source, but we have provided the scientific info to [the] government who have then used a number of other sources to piece together the conclusions", Mr Aitkenhead told Sky News.
"It is our job to provide the scientific evidence of what this particular nerve agent is, we identified that it is from this particular family and that it is a military grade, but it is not our job to say where it was manufactured", Aitkenhead said.
He reiterated that the substance could not have come from Porton Down.
Russia's European Union ambassador Vladimir Chizhov noted in an interview with the BBC last month that the British research lab is only 11km from Salisbury, insinuating that it may have been the source of the nerve agent.
Vladimir Putin won the Russian election last month by a landslide to give him a record fifth term as president.
Britain has accused Russian Federation of involvement in the March 4 nerve agent attack on former double agent Sergei Skripal and his daughter, the accusations Russian Federation has vehemently denied.
The defence research facility, which identified the substance in Salisbury as Novichok, said it was likely to have been deployed by a "state actor".
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There are doubts that rogue agents could have carried out the attack without approval from the top levels of Russian government.
In a statement released Tuesday, the OPCW confirmed that its Executive Council had received the request from the Russian representative to the group and that, "the confidential meeting will start at 10.00 am (0400 Eastern) at the OPCW's headquarters in The Hague". He added Moscow had "no outstanding issues" against the 66-year-old Skripal.
Downing Street's statement comes after Evgeny Buzhinsky, a former Russian general, told British media the diplomatic fallout from the poisoning could get "worse than the Cold War" and trigger a "real war".
But perhaps the more vehement response came from Russian officials, who have denied the allegations that the Kremlin was involved in the attack.
The meeting on Wednesday has been called by Russian Federation to "address the situation around allegations of non-compliance" with the chemical weapons convention made by the United Kingdom against Moscow.
The 'secret bank account' was disclosed by Sergei's niece Viktoria Skripal, 45, who aims this week to travel to meet Yulia in hospital in Salisbury.
"As for the other countries, everything will also be symmetrical in terms of the number of people from their diplomatic missions who will be leaving Russian Federation, and for now that's pretty much it", said Foreign Minister Sergei Lavrov.
"We have an interest in a full investigation and want Russian Federation to be allowed to take part in that investigation", he said.
On Tuesday, a spokesperson for the UK's Foreign and Commonwealth Office reiterated it was considering requests for consular access in line with its obligations under global and domestic law, which include the rights and wishes of Yulia Skripal.