Russia defied threats of new Western sanctions Friday in a staring match over the poisoning of Alexei Navalny, as NATO demanded Moscow uncover its Novichok nerve agent programme. A new crisis in ties between Russia and the West broke out after Germany said this week there was “unequivocal evidence” that President Vladimir Putin’s top foe had been poisoned using the infamous Soviet-era nerve agent Novichok. Western leaders and many Russians have expressed horror at what Navalny’s allies say is the first known use of chemical weapons against a top opposition leader on Russian soil. The 44-year-old lawyer fell ill on a Siberian flight last month and was evacuated to Germany for treatment. He has been in an artificially induced coma for the past two weeks. The Kremlin has denied the Russian state is to blame, and on Friday Putin’s spokesman indicated that Moscow would not budge. “A whole number of theories including poisoning were considered from the very first days,” Dmitry Peskov told reporters. “According to our doctors, this theory has not been proved.” “We have nothing to hide,” declared Foreign Minister Sergei Lavrov.