Police cordons are still in place in Salisbury, a month after the poisoning that caused a diplomatic incident between the two countries.
"We didn't do it, we're not guilty", Nebenzia said.
Thursday's Security Council meeting on the attack was at Russia's request.
"The Foreign Secretary was making clear Porton Down is sure the nerve agent was a novichok", she said.
In the same vein, French delegate to the United Nations Francois Delattre said France would never allow impunity for those who used chemical weapons, adding that Russian Federation must be part of the solution and immediately act responsibly.
Doctors caring for Skripal gave an update on his condition on Friday.
The improvement of Skripal and his daughter marks the latest twist in an affair that British and Russian diplomats have variously compared with Sherlock Holmes and Agatha Christie mysteries.
British Foreign Office said Yulia has refused to take up any help offer from Russian Federation.
But the Foreign Office on Wednesday deleted a tweet from last month that said scientists at Britain's defense research facility, the Porton Down laboratory, had identified the substance as "made in Russian Federation". As Yulia herself says, her strength is growing daily and she can look forward to the day when she is well enough to leave the hospital.
Russia's state television has aired a recording of an alleged phone conversation, which it says took place between one of the two poisoning victims in Britain Yulia Skripal and her cousin.
"Everything is fine, everything is fixable, everyone is getting better, everyone is alive", they quoted her as saying in the call. She adds that "Everyone's health is fine, there are no irreparable things" and that she will be discharged from hospital soon.
South Africa beat Australia, take series 3-1
A review showed Lyon to be short as De Kock removed the bails, a woeful ending that summed up Australia's day, Test and series. Markram went on to score two centuries and finish the leading run-scorer of the four-Test series, tallying 480 runs at 60.
Russian lawmaker Konstantin Kosachev, the chairman of the global affairs committee of Russia's upper house of parliament, said the sanctions were "baseless and unfriendly".
Moscow has denied the accusations and has seized on the ambiguities surrounding the investigation in an aggressive campaign to discredit British authorities.
On Wednesday, Russia lost its call for a joint inquiry to be held into the poisoning at a meeting of global watchdog the Organisation for the Prohibition of Chemical Weapons.
"They're not giving me a visa, they keep postponing it", she said.
That prompted even some allies to say London needs to provide more evidence of Russian culpability.
Russian Federation has warned Britain is "playing with fire and will be sorry" over the Salisbury attack after it emerged Yulia Skripal's strength is "growing daily".
The incident has drawn comparisons to the 2006 death of former KGB agent Alexander Litvinenko after drinking radioactive tea.
Former spy Sergei Skripal and his daughter were found unconscious in early March.
Russian Ambassador Alexander Yakavenko said the embassy is now getting its information from the mainstream media, after being locked out of Britain's investigation.
The press secretary for the Russian Embassy in the United Kingdom. "My question is why is it happening here?"