The entire UN was a construct of the post WW2 global reconfiguration. The permanent members: USSR (Russia), China, UK, USA, and France were the major countries that contributed significantly to the defeat of the Axis. The military contribution of British India was not significant compared to others, 87,000 died from military action and the rest were from famine.
Military deaths from WW2
USSR: 9-11 million
China: 3-4 million
USA: 400,000
UK: 380,000
Poland: 240,000
France: 210,000
India: 87,000
The permanent seat is not about the size and population of your country but
how important it is in the formation of the global architecture, much of which was founded on blood and sacrifice. India has a lot of people and its population will likely surpass China in the near future, has nukes and a medium sized economy but other than that it has yet to prove itself worthy of the seat.
It needs to prove to the world that it can form the global architecture for the next era (why else would P5 accept another member?), based on real action not rhetoric. That is the way to make other country feel it is acceptable for India to have a seat. As of now, you can't really blame the P5 for not wanting another country like India. What sacrifice has it contributed in shaping the next era and what results does it have to show for it? I don't like being so blunt as it may hurt the feelings of some aspirational ones but the reality is that India has yet to earn its place.
The advanced countries rejected China in joining the international space station project for many years but it will soon launch its own independent space station. There is no free meal in international relations, you only get what you put into it, rarely do you get things you don't deserve.
I'm not saying it is impossible for India to become a member of the P5 (P6) but it must contribute much more to the global architecture. Currently it's doing very little, Argentina contribues more funding to UN. PRC's bid into the UN to replace the ROC was the unconditional support and funding of African and other third world nations. China at the time of the 60s were starving in worse famines than African nations but still built rail roads and other infrastructure projects along with medical support for African nations, without asking for anything in return. In history what country was willing to do that under those conditions? This resulted in gaining support and respect from these countries to support the PRC in UN. This is also why propaganda against Chinese interests in Africa won't work and why African nations in general accept Chinese investment above others, our forefathers sacrificed to better the lives of people we are not related to even when we were starving. What
actual benefit is India bringing to the world to make others respect it? not just asking others for support but real action to better others. So far its asking for too much and doing too little.
UN budget contributions:
http://www.un.org/ga/search/view_doc.asp?symbol=ST/ADM/SER.B/955
