Marina Litvinenko has described her final conversation with her dying husband, Alexander, telling a public inquiry that his last words to her from his radioactive hospital bed were: “I love you very much.”

Mrs Litvinenko said her husband’s condition worsened dramatically in the last couple of days before his death on 23 November 2006. He was suffering “pain all over his body”, his hair had fallen out and he was “speechless for most of the time”, she said.

After spending the day at his side in the intensive care ward of University College hospital on 22 November, Mrs Litvinenko said, she went home to look after their 12-year-old son, Anatoly. “I started to feel guilty I was leaving him. I said: ‘Don’t worry, tomorrow morning I’ll come to the hospital.’”

Her husband smiled at her, she recalled, and said: “I love you very much.”

Mrs Litvinenko said she tried to reassure her husband, joking: “Oh finally. I haven’t listened to this for a long time,” and telling him: “Everything will be fine. See you tomorrow.”

“Those were his last words,” she told the high court inquiry into her husband’s murder.

Mrs Litvinenko said the hospital called her soon after she returned home to say her husband’s conditioned had deteriorated. She rushed back to discover a crash medical team had resuscitated him after he suffered a heart attack.

She spent the following day by his side, she said, while he was unconscious. She went back to her home in Muswell Hill, north London, only to be recalled by the hospital a second time, when Anatoly was “already in his pyjamas”.

The Litvinenkos’ friend and neighbour Akhmed Zakayev drove her to the hospital, where she was ushered into a side room.

“The doctor said unfortunately Sasha has passed away. After that he asked would you like to see Sasha? I said yes of course,” Mrs Litvinenko said.

“When we went to his room it was different. We didn’t need protective gloves. I could touch him. I could kiss him. Nobody said it was dangerous.”

Mrs Litvinenko said Anatoly saw his dead father “for half a minute maximum” and then fled the room. The pair of them returned home stunned, exhausted and upset. Detectives then called her on her mobile phone and asked for an urgent meeting.

She said she was reluctant but they insisted. She said the police told her: “We know what happened to your husband and what was used. It was radioactive polonium-210.” The officers told her she had to leave her home immediately. “We were given 30 minutes to evacuate,” she said.

Litvinenko was poisoned on 1 November 2006, after meeting two Russian contacts – Andrei Lugovoi and Dmitry Kovtun – in a Mayfair hotel. They allegedly slipped the polonium into Litvinenko’s tea. The inquiry heard last week that the pair had made an earlier, unsuccessful, attempt to poison him on 16 October.

The Litvinenko inquiry will hear evidence about the murder of former KGB agent, Alexander Litvinenko. Watch our video explainer about what the inquiry will try to establish. Guardian

Mrs Litvinenko said on that occasion her husband had returned from a meeting with Lugovoi and Kovtun in good spirits. He ate a spicy meal, and then later that evening complained of “feeling unwell”. He vomited.

The second occasion, on 1 November, was immediately more serious, she said. “Suddenly he started to feel unwell. He just vomited.”

Litvinenko’s condition got worse. She called an ambulance in the early hours of 3 November – the paramedics diagnosed flu – and again later the same day. Litvinenko was admitted to Barnet and Chase hospital in north London. He was exhausted, unable to eat and struggling to breathe, she said.

At this point, Mrs Litvinenko said, she was confident her husband would recover, and at first in hospital his condition slightly improved. On 13 November, however, he abruptly worsened.

“I was absolutely devastated. It was the first time I realised his hair was starting to fall out. I tried to hold his head. His hair was on my glove.” Mrs Litvinenko said she demanded to know what was happening to her husband.

The High court was previously told that Litvinenko worked from 2003 as a “consultant” for British intelligence, supplying MI6 with information on the links between Kremlin officials and the Russian mafia. The inquiry heard on Tuesday that MI6 had given Litvinenko a secret British passport in a false name. His MI6 alias wasn’t revealed.

Mrs Litvinenko said her husband’s MI6 handler “Martin” had also visited him in University College hospital just days before his death. She said it was obvious “Martin” was Litvinenko’s MI6 contact. “[At this point] nobody was allowed into the hospital to see Sasha,” she explained.

Giving evidence Litvinenko’s son Anatoly – now 20 – said he had visited his father several times in hospital. “I thought he would recover,” he said. His death left him numb, he said. He added that he subsequently blanked out the “emotionally challenging” events surrounding his father’s death, which “overlapped with my adolescence.”

In its aftermath “my relationship with my mother got stronger,” he said, in a witnesses statement read to the court. He added: “After my father’s death we became closer. She has always been my friend. She’s been my rock all these years. I have tried to do my best to fulfil my father’s last wish by looking after her.”

The inquiry also heard how Litvinenko had blamed Vladimir Putin personally for the murder of the Russian journalist Anna Politkovskaya, shot dead in October 2006. A video was played of Litvinenko’s speech to a media event at the Frontline club in west London, in which he said only Putin had the power to authorise her murder.

Mrs Litvinenko said she had been present when her husband made his deathbed statement that blamed Putin for his murder. She had initially opposed the photograph taken of him, bald, proud and defiant, but said he had approved this too.

Visitors to Litvinenko’s deathbed included Boris Berezovsky and Litvinenko’s father, Walter, who flew in from Moscow. Litvinenko told his father he had converted to Islam. Mrs Litvinenko said Walter replied: “It doesn’t matter. At least you’re not a communist.”

The inquiry continues.