When Winston Smith finds Goldstein's book, in that is written the principles of doublethink (The term doublespeak is not actually used in the book). The famous lines "Ignorance is Strength" etc. But the Ministry of Truth does not broadcast these to the people. The Ministry of Peace does not broadcast "War is peace". It broadcasts "We have always been at war with Eastasia." A big lie.
My point is it doesn't have to be the principles of doublespeak as outlined in Goldstein's book to be doublespeak. The Ministries application of the principles of doublespeak appear to the populace as a big lie.
"But it means also the ability to BELIEVE that black is white, and more, to KNOW that black is white, and to forget that one has ever believed the contrary. This demands a continuous alteration of the past, made possible by the system of thought which really embraces all the rest, and which is known in Newspeak as DOUBLETHINK." -- George Orwell