Mr Saunders, 40, was forced to abandon his mission to cross Antarctica unassisted after ‘ferocious’ weather conditions left him without enough food to complete his journey.
He had attempted the trek in memory of his friend Lieutenant Colonel Henry Worsley, who died on an expedition to traverse the Antarctic alone last year.
Mr Saunders aimed to spend 65 days travelling more than 1,000 miles across Antarctica, but was forced to cancel the trip when he arrived at the South Pole on Thursday, after 52 days.
He had just 13 days of food for the remainder of the expedition, which he expected to last a minimum of 17 days if conditions were perfect.
Mr Saunders said he had made a promise to Lt Col Worsley that he would ‘get home in one piece,’ and writing on his blog after abandoning the trek, he referenced Shackleton’s renowned retort after giving up his own attempt to reach the pole in 1909.
"Are you a lion or a donkey?" his wife Emily asked him on hearing of the failure. "Better a live donkey than a dead lion," Shackleton replied.
Speaking of his own defeat, Mr Saunders said: “I type this with bittersweet feelings. This is a high-stakes, high-consequence environment and, paradoxically, one where prudence often trumps derring-do and bravado, as Shackleton summed up in his line about lions and donkeys.
“Standing here with less food for the remainder of my journey than I’d planned, with a safety margin that I felt was too slim, I have decided this time to end my expedition at the Pole.
"I made a promise to Henry to get home in one piece. As much as I am determined to finish this trip for him, I need to make my decision based on safety and not let my own determination cloud my judgment.
"I don't think Henry would be telling me to go for it given my concerns about the diminished safety margin. It feels like the most respectful thing I can do after Henry's fate is to be prudent and safe."
Mr Saunders said he was forced to give up after realising his rations could not last the remaining journey, and that air rescue would be impossible on the final stretch of the adventure.
Despite ending his quest, Mr Saunders is only the third person in history - and the only Briton - to have skied by himself to both the North and South poles.
“I'm proud that I’ve always aimed high, I’m proud that I’ve been willing to fail publicly, time and again as I’ve fallen short of some of my biggest goals,” he added.
“Right now I’m feeling happier and more content than I thought I’d be, but perhaps the regret might follow later.”
As an experience adventurer, Mr Saunders knew that the mission could end in failure. His close friend Lt Col Worsley died of multiple organ failure after collapsing 913 miles into his Antarctic crossing attempt in January 2016.
With just 30 miles left to go, the former SAS soldier sent a heart-rending final message, telling the world: “My journey is at an end….my summit is just out of reach.”
Mr Saunders had planned to pass the South Pole with at least 20 days of rations in hand, ahead of the 17 day final push. As part of the rules he was not allowed to take on more supplies at the pole.
But treacherous conditions mean he fell dangerously behind.
“I’ve never known the conditions so bad,” he told The Telegraph before he reached the Pole. It’s completely disorientating and really hard to navigate, incredibly tough.”
In 2014, Mr Saunders completed the longest polar foot journey in history in company with Tarka L’Herpiniere, becoming the first team to complete the return journey - 3,700 miles and 105 days - to the South Pole from Ross Island which defeated Captain Scott in 1912.
Shackleton had failed in the same attempt when his ship was crushed in the ice of the Weddell Sea shortly after he arrived, and he and his 28-man crew spent the next two years in an epic fight for survival.