Iravatham Mahadevan of the Indus Research Centre, Roja Muthiah Research Library, Chennai, writes:
Apropos the rejoinder by Mr. A.B.K. Prasad, Chairman, Andhra Pradesh Official Languages Commission (The Hindu, May 4, 2008), regarding the dates of earliest inscriptions and literary works in Old Tamil and Old Telugu, I reproduce below the relevant passages from The Dravidian Languages (Cambridge University Press 2003) by Bh. Krishnamurti, world’s leading authority on Dravidian languages and himself a native speaker of Telugu.
Tamil: “Cave inscriptions [some 76] in Tamil-Brahmi script were found in Madurai and Tirunelveli districts ca. second century BC. The first known work, Tolkappiyam, is a treatise on grammar and poetics ascribed to the early pre-Christian era, presupposing a large body of literature before it, available in the form of anthologies.” (p.22)
Telugu: “Telugu place names occur in Prakrit inscriptions from the second century AD onwards. The first Telugu inscription is dated 575 AD from Erragudipadu of the Kadapa district by a prince of the Coda dynasty; the first literary work, a poetic translation of a part of the Mahabharata, belongs to the eleventh century AD.” (p.23)