Letters flew between Shackleton, Keltie, and Scott.
Shackleton had been bitterly offended by Scott's account of the southern journey in The Voyage of the 'Discovery' in October 1905, which Shackleton saw as implying weakness on his part, and that having to carry Shackleton on the sledge caused the distances to be shorter than they might have been. All three members of the southern party -- Scott, Wilson, and Shackleton -- had developed scurvy, but Shackleton was the only one who had been sent home early, which Shackleton saw not only as a personal criticism but as damaging to his reputation as an explorer and the possible leader of an expedition.
Shackleton said now that he had learned of Scott's plans only when he asked George Mulock, who had replaced him on the Discovery, to join him, and found that Mulock had already agreed to accompany Scott. "I took the letter to the Geographical Society and saw Kelty [sic]. I said 'What is the meaning of this?' Kelty said 'Oh! Mulock has let the cat out of the bag.' I said 'What do you mean?' I said 'Is Scott going to go?' He said 'Yes.'" 
Scott was furious and wrote to Keltie, "You do not say that you told him that I contemplated getting up an expedition, but it is impossible to imagine that you omitted to mention it when you saw him. That fact must therefore be that Shackleton deliberately worded his notice so as to forestall me -- I would have not believed it of any of my own people -- and since it is so I cannot express my condemnation of such an act too strongly." 
Keltie replied, "Your letter makes me feel very unhappy. I feel rather sorry now that when Shackleton spoke to me first about his expedition and told me that he was going to put it in the papers next day that I did not tell him what were your intentions.... But then I thought that you wanted to keep the whole matter absolutely secret.... Of course you will understand that my position here is a difficult one.... I think that you will admit that we could not ignore his expedition altogether."
"He has evidently been quite upset," Keltie went on, "by your letter and the letter he has had from Barne, he told me he has not slept for four nights. He has evidently been thinking over alternatives. He talked of the Weddell Sea, and landing there and trying to make his say to the Pole, then he thought of making King Edward VII Land his base of operations, and leaving the old Discovery quarters to you and even hinted that he might turn his expedition to the North Pole.... As to Shackleton's capacity as a leader and his staying powers, I think you and I take the same view. He looks strong enough, but it is clear that he is not absolutely sound, and Heaven knows what may happen if he starts on his journey Pole-wards." 
"As to his chance of success I do not like to express an opinion. On the one hand he has lots of energy & he may select his people well -- on the other I personally never expect much in this sort of work from a man who isn't straight -- it is the first essential for the co-operation necessary for such a venture -- of course also Shackleton is the least experienced of our travellers and he was never very thorough in anything -- one has but to consider his subsequent history to see that -- he has stuck to nothing & you know better than I the continual schemes which he has fathered." 
Shackleton, however, wrote to Barne, "I would rather lose the chance of making a record that do anything that might not be quite right," and a few days later that he could see that "as Britishers, the position is clear." 
Scott replied to Shackleton, "I am sorry to have done you this injustice and I think it right to tell you how it came about. I ... have the relief of knowing that you did not intentionally wreck my plans and the thought that you had done so was very distressing to me, for it seemed an action of which an old Discovery should have been incapable and one that surprised me beyond measure in you. I apologise for having thought you guilty of it. As to Keltie we must now draw our own conclusions -- His silence seems to have been deliberately calculated to make trouble -- he must have known that I should protest and think evil things of you and that you would be deeply troubled, as I gather you are ... neither of us I expect is likely to forget it." 
Scott wrote to Keltie a few days later, "I confess your silence appears to me inexplicable. Now that I know the facts I must of course acquit Shackleton of want of loyalty but I cannot think that you acted a friendly part.... It is beyond me to guess what was in your mind.... I confess I am at a loss to find your motive and being a plain dealing person I have been exceedingly hurt by your act." 
Wilson was already taking on the role of peace-maker between Scott and Shackleton, who wrote to him, "I do not agree with you, Billy, about holding up my plans until I hear what Scott considers his rights. There is no doubt in my mind that his rights end at the base he asked for, or within reasonable distance of that base. I will not consider that he has any right to King Edward the Seventh's Land, and only regard it as a direct attempt to keep me out of the Ross quarter if he should ever propose such a thing. I have given way to him in the greatest thing of all, and my limit has been reached.... [Just] as well might Borchgrevink have objected to Scott wintering anywhere within a radius of 500 miles of Cape Adare." 
"The question now," Scott wrote to Shackleton, "is what you intend to do? On the one hand I do not wish to stand in the way of any legitimate scheme of yours -- on the other it must be clear to you now that you have placed yourself directly in the way of my life's work -- a thing for which I have sacrificed much and worked with steady purpose -- Two expeditions cannot go to the same spot either together or within the compass of several years -- If you go to McMurdo Sound you go to winter quarters which are clearly mine.... I do not need to remind you that it was I who took you South or of the loyalty with which you all stuck to one another or of incidents on one voyage or of my readiness to do you justice on my return." 
There were in fact rumours that the Pole Henryk Arctowski, oceanographer from the Belgica expedition and shipmate of Amundsen's and Cook's, was planning to return to the Ross Sea.
Scott, still unwilling to show his hand publicly, wrote to Keltie, "If you in consultation with others think it wise to announce a change of Shackleton's plan and a hint as to my own I am willing that you should do so presuming it is solely to show the world that England intends to operate in the Ross Sea -- If you think no such statement is necessary but it will be sufficient to inform foreign rivals more privately it would be a course better suited to my views." 
 Ernest Shackleton, letter to R.F. Scott, 27 February, 1907, quoted by David Crane in Scott of the Antarctic (New York : Knopf, c2005), p.302.
 R.F. Scott, letter to Scott Keltie, undated, quoted by David Crane in Scott of the Antarctic (New York : Knopf, c2005), p.302.
 Scott Keltie, letter to R.F. Scott, 1 March, 1907, quoted by David Crane in Scott of the Antarctic (New York : Knopf, c2005), p.301.
 R.F. Scott, letter, [addressee not given], 2 March, 1907, quoted by David Crane in Scott of the Antarctic (New York : Knopf, c2005), p.301-302.
 Ernest Shackleton, letters to Michael Barne, 5 March and 7 March, 1907, quoted by David Crane in Scott of the Antarctic (New York : Knopf, c2005), p.301.
 R.F. Scott, letter to Ernest Shackleton, 7 March, 1907, quoted by David Crane in Scott of the Antarctic (New York : Knopf, c2005), p.302-303.
 R.F. Scott, letter to Scott Keltie, 11 March, 1907, quoted by David Crane in Scott of the Antarctic (New York : Knopf, c2005), p.303.
 Ernest Shackleton, letter to E.A. Wilson, 11 March, 1907, quoted by David Crane in Scott of the Antarctic (New York : Knopf, c2005), p.303-304.
 R.F. Scott, letter to Ernest Shackleton, 26 March, 1907, quoted by David Crane in Scott of the Antarctic (New York : Knopf, c2005), p.303.
 R.F. Scott, letter to Scott Keltie, 26 March, 1907, quoted by David Crane in Scott of the Antarctic (New York : Knopf, c2005), p.304.