Here are the Facts from the Indian perspective.
Nehru got FOUR foreign offers in total for a UNSC seat. Twice by US in 1950 and 1955. Once by Chinese rebels and once by USSR.
The First offer was in 1950.
In a letter to Nehru dated 24th August 1950,
Indian Ambassador to US and Nehru's sister Vijayalakshmi Pandit reveals that US State department made a proposal to India for UNSC seat. Those were the days of Cold War and US was looking at a potential ally in India.
How was this Possible ? Especially when people claim that there has been NO CHANGE in the UN composition since it was first set up ?
There HAS BEEN a change in UN composition. In 1950, PRC was blocked from taking Chinese seat at UN. In response Russia walked out. These events gave a scope for a new member.
To this Rare opportunity
Nehru wrote a response to this letter on August 30 in which He unequivocally denied the offer. He said the UNSC seat would break "the impeccable relations between India and China".
He further said "it would be an affront to China" and he would "press for China's admission in UNSC"
From 1951, Nehru worked constantly to ensure china go the permanent council seat at the UN.
So much so that Dr. Ambedkar who was one of the Founding members o f the Indian constitution wrote this in Frustration.
Here is one Indian Newspaper of that time, highlighting Nehru's plea for UN(UNSC) seat for Peking (China).
Here is a scholarly work by Anton Harder who was a PhD candidate in the International History Department of the London School of Economics. His dissertation is on Sino-Indian relations from 1949-1962. "Not at the cost of China"
https://www.wilsoncenter.org/sites/default/files/cwihp_working_paper_76_not_at_the_cost_of_china.pdf
The Second offer came in 1955.
It was initially made by Soviet Premier Nikolai Bulganin’s as a offer of a permanent seat on the United Nations Security Council in 1955. This was made as a feeler to test India and proposed to make India the SIXTH member of the Security council.
Jawaharlal Nehru again rejected the Soviet offer to propose India as the sixth permanent member of the Security Council and insisted that priority be given to China’s admission to the United Nations.
Their conversation is recorded and published in the selected works of AG Noorani.
[Nikolai] Bulganin: Regarding your suggestion about the four power conference we would take appropriate action. While we are discussing the general international situation and reducing tension, we propose suggesting at a later stage India’s inclusion as the sixth member of the Security Council.
JN [Jawaharlal Nehru]: Perhaps Bulganin knows that some people in USA have suggested that India should replace China in the Security Council. This is to create trouble between us and China. We are, of course, wholly opposed to it. Further, we are opposed to pushing ourselves forward to occupy certain positions because that may itself create difficulties and India might itself become a subject to controversy. If India is to be admitted to the Security Council, it raises the question of the revision of the Charter of the UN. We feel that this should not be done till the question of China’s admission and possibly of others is first solved. I feel that we should first concentrate on getting China admitted. What is Bulganin’s opinion about the revision of the Charter? In our opinion this does not seem to be an appropriate time for it.
There was also an offer from the US in the same time frame for a permanent seat for India. This is made clear by Nehru's own letter on August 2 1955.
Nehru in his letter to Chief Ministers clearly mentions there was indeed an informal offer from US for a UNSC seat. Nehru denied it because he didn't want to take the seat "because it would be unfair to a great country like China"
This letter can be accessed online.
It is available on Page 237 of Jawaharlal's Nehru's "Letters to the Chief ministers Volume 4 (1947-1964)", Oxford university Press. Government of India 1988
Check for page 237 in this link
https://ia801606.us.archive.org/20/items/in.ernet.dli.2015.54646/2015.54646.Letters-To-Chief-Ministers-1947-1964-Vol-4_text.pdf …
Despite this, Nehru shamelessly LIED on the Floor of the Parliament and claimed there was no such offer. He did this because to admit to the offer and to then admit he rejected it would have be political suicide.
On 27 September 1955 in Parliament, Nehru categorically denied that a UNSC seat was ever offered to India. "There has been no offer, formal or informal, of this kind".
Though just a MONTH earlier his letter to the CM's admits the opposite.
The worst part is that even in 1963, a year after China invaded India. PM Nehru's sister - leader of India's delegation to UN - said India STILL supports China's admission to the United Nations as a "matter of principle".
Today, China spares no effort to oppose India at the UN. As a "matter of principle".
Also as a side note, here is a picture of some Indians in China. The picture shows Naga separatist leaders at the Great Wall of China, 1960s. China has created, supported & armed insurgencies & terrorism in India for over half a century.
So china's support to Azhar Mahmood should not come as a surprise to anybody.