Thousands of people have sent messages of love and support to Harry Leslie Smith, the 95-year-old political commentator and second world war veteran, who is critically ill in hospital in Canada after a fall.

The former RAF pilot is believed to have been taken ill with pneumonia after the accident. His son John has been using his father’s Twitter page to post updates on his condition, attracting thousands of messages of support from back home in the UK.

The Barnsley-born activist, who has been an outspoken campaigner against austerity and the privatisation of the NHS, is no longer in an acutely critical condition but is still very ill. On Wednesday he was visited by his grandsons in hospital and he was eating and drinking.

The update from the icu Dr is Harry is moving in the right direction still critical but not acutely. — Harry Leslie Smith (@Harryslaststand) November 21, 2018

The Labour leader, Jeremy Corbyn, and the UN Refugee Agency in Canada are among thousands of people and organisations who have sent their best wishes to Smith.

John Smith first raised the alarm on Tuesday, posting from his father’s account: “Harry is in A&E and not in a good way. He asked me to inform you in case things don’t work out. I will keep you posted.”

On Wednesday he said his father had been allowed to have a cup of tea, eat a small amount of toast and receive a visit from his grandsons, to whom he had quipped that “he’d rather have a shandy than the small amounts of water he’s getting”.

After being examined by the icu doctor, Harry exclaims, " I can assure you, I am not ready to die because I have too much work to do." — Harry Leslie Smith (@Harryslaststand) November 21, 2018

In response to the news of Smith’s illness, Corbyn posted: “Very sorry to hear this. Please pass on my best to Harry. We need him to get well soon as the National Health Service, and our movement, needs him.” The deputy Labour leader, Tom Watson, wrote: “You are in my thoughts Harry.”

Joanne Harris, the author of Chocolat, wrote: “Thinking tonight of @Harryslaststand, a firebrand and a hero.” The actor Adrian Lester described Smith as “an inspiration”.

Smith initially went into hospital on Tuesday, tweeting himself: “Bugger of a day, had a fall and now I am in hospital. It’s nothing just low blood pressure, but signing off for the next few hours.”

After the huge show of support for his father, John Smith tweeted: “He sleeps and when he wakes for a moment I tell him about the love flowing out from Twitter. ‘Tell them I love them all.’”