India has criticised the international community for failing to prevent the spread of nuclear weapons.
Singh was speaking ahead of a nuclear proliferation conference
Foreign Minister Natwar Singh said much of the proliferation tended to emanate from its South Asian neighbourhood.
India has long criticised the United States for overlooking Pakistan's alleged involvement in spreading nuclear technology.
Mr Singh's comments came three days after the US said it would sell F-16 jets to India's nuclear rival Pakistan.
Washington has also offered India combat planes, an offer Delhi said it would consider.
But ahead of an international conference on the Nuclear Non-Proliferation Treaty (NPT), Mr Singh said the world's leading nuclear powers had not been serious in its efforts.
"Unfortunately, even today, we see the same inconsistencies in approach with selective focus on the recipients of such clandestine proliferation but not enough attention on the sources of supply," Mr Singh said.
Pakistan's disgraced nuclear scientist, AQ Khan, is believed to have supplied nuclear technology to Iran, Libya and North Korea.
Last week Pakistani President Pervez Musharraf said Islamabad was considering sending nuclear parts to a UN watchdog to help it investigate whether Iran was developing atomic weapons.
The US on Friday said it was offering combat planes to both India and Pakistan.
The two rivals, who went nuclear in 1998, have fought three wars since independence in 1947.
India warned that the decision to sell F-16s to Pakistan risked creating an arms race.
But on Monday, President Musharraf applauded the US decision: "This will make a strategic difference. This will tremendously increase our defence capability and the strategy of defensive deterrence."
The US said it was also allowing US defence companies to bid for a large Indian order for combat aircraft and said it was also considering offering India technology for civilian nuclear energy.
"This is the first time we have received an offer from USA," Defence Minister Pranab Mukherjee said.
"Naturally, when the offer is there, it will have to be actively considered by the government of India keeping in view the requirements of our armed forces."
Media reports said both the F-16 and the multi-role F-18 combat aircraft were on offer.
US Secretary of State Condoleezza Rice said America was looking to "solidify and extend relations" with both India and Pakistan at a time when Washington enjoyed good relations with both countries.
The decision to sell warplanes to Pakistan also marks a change in US policy, which blocked the sale of F-16s in 1990 over Pakistan's nuclear weapons programme.
The revived sale will form part of a five-year, $3bn assistance programme.