At least 17 people die in pain every day in Britain despite the best efforts of medical staff.
The shock findings by the Office of Health Economics have led to campaigners stepping up calls for assisted dying to be legalised.
It found even if all patients had access to the level of care in hospices, 6,394 people a year would still suffer severely in their final three months.
Withdrawal of treatment, sedation and choosing to stop food and drink to hasten death is legal in the UK.
However pro-assisted dying campaigners and bereaved families say, in some cases, these limited options rob people of pain free and dignified deaths.
Last year in a Mirror poll three in four backed allowing assisted dying to end suffering.
Emma Cozzi, 31, from Portsmouth, lost mum Ruth, 58, who became terminally ill with a flesh-eating bug in March 2016. Ruth died after 11 days in agony.
Emma said: “The pain got worse and worse. Hospital staff upped her relief but it never completely removed it. She’d groan in her sleep.”
Valerie Jones’s sister Jo Valla, 66, spent three-and-a-half weeks in agony at the end of her fight with ovarian cancer.
Val, 65, of Morecambe, Lancs, said: “She wanted staff to euthanise her. She would whelp like a dog. It wasn’t humane keeping her alive.”
MP Nick Boles, Chairman of the All-Party Parliamentary Group for Choice at the End of Life, said: “To deny [assisted dying] to people who can’t be helped by palliative care is a moral outrage.”
The Ministry of Justice said: “Any change in the law is for Parliament rather than Government policy.”
More about this report on Channel 4 news on Monday night at 7pm.
