Jawahar Lal Nehru (1889-1964) was the first and longest-serving Prime Minister of India. He was also a well-known atheist. His criticism of religion, especially organized religion, has supplied many rich sources of quotes . Here are just a few to establish his atheism.
"What the mysterious is I do not know. I do not call it God because God has come to mean much that I do not believe in. I find myself incapable of thinking of a deity or of any unknown supreme power in anthropomorphic terms, and the fact that many people think so is continually a source of surprise to me. Any idea of a personal God seems very odd to me." -- Autobiography (1936; 1949; 1958)
"Religion is not familiar ground for me, and as I have grown older, I have definitely drifted away from it. I have something else in its place, something older than just intellect and reason, which gives me strength and hope. Apart from this indefinable and indefinite urge, which may have just a tinge of religion in it and yet is wholly different from it, I have grown entirely to rely on the workings of the mind. Perhaps they are weak supports to rely upon, but, search as I will, I can see no better ones." -- Letter to Mahatma Gandhi (1933), as quoted in "Nehru's Faith" by Sunil Khilnani, in The New Republic (24 May 2004), p. 27
"Religion merges into mysticism and metaphysics and philosophy. There have been great mystics, attractive figures, who cannot easily be disposed of as self-deluded fools. Yet, mysticism (in the narrow sense of the word) irritates me; it appears to be vague and soft and flabby, not a rigorous discipline of the mind but a surrender of mental faculties and living in a sea of emotional experience. The experience may lead occasionally to some insight into inner and less obvious processes, but it is also likely to lead to self-delusion." -- Autobiography (1936; 1949; 1958)