It comes amid speculation about the Russian leader’s health in recent days, though the Kremlin has categorically denied that Mr Putin is ill. Valery Solovei – a known Putin critic – has claimed the head of state has cancer.
It follows an earlier assertion by Mr Solovei that Mr Putin may have Parkinson’s Disease, as first reported by The Sun.
Now, the Putin critic and political analyst is making further claims about the Russian leader’s health.
Mr Solovei referred to sources within the Kremlin with whom he allegedly has contact.
He told The Sun on Friday that Mr Putin, 68, had two health conditions, adding “one is of psycho-neurological nature, the other is a cancer problem.”
He said: “If anyone is interested in the exact diagnosis, I’m not a doctor, and I have no ethical right to reveal these problems.”
Mr Solovei, who is a former head of the PR department at the Moscow State Institute of International Relations, also claimed Mr Putin had surgery in February this year.
Meanwhile, Mr Solovei has suggested a number of other prominent Russian figures are said to be vying for the presidency.
They include Mr Putin’s 34-year-old daughter Katerina Tikhonova, who currently leads an AI programme.
Others are said to be Dmitry Medvedev, who resigned as Prime Minister earlier this year, and Dmitry Patrushev, the country’s Agriculture Minister and Russian Agricultural Bank CEO.
Kremlin spokesman Mr Peskov had already denied earlier this month that Mr Putin had plans to step down in the near future.
This week, Russia’s lower parliamentary house the Duma backed a bill which would give Mr Putin and his family immunity from criminal prosecution even if he were to step down as president.
The bill forms part of a number of amendments to the Russian constitution which were agreed in July this year.
Other changes include allowing Mr Putin to hold the presidency for two more terms.
His current term is due to end in 2024, meaning he will have been in power for around 24 years.
Alexei Navalny, one of Putin’s more prominent critics and an opposition leader, tweeted: “Why does Putin need an immunity law now?”
Mr Navalny has been gradually recovering after being poisoned by a nerve agent earlier this year whilst on a flight in Siberia.
German medical investigators concluded chemical agent Novichok was used. The Kremlin has widely been blamed but denies any involvement.