The White Poppy was first produced by the Co-operative Women's Guild in 1933, but the idea started brewing around 1926, when the "No More War Movement" suggested that the British Legion red poppies have the words "No more War" printed on their centre rather than "Haig Fund".
The Peace Pledge Union website says:
the Co-operative Women's Guild who in 1933 produced the first white poppies to be worn on Armistice Day (later called Remembrance Day). The Guild stressed that the white poppy was not intended as an insult to those who died in the First World War - a war in which many of the women lost husbands, brothers, sons and lovers. The following year the newly founded Peace Pledge Union joined the CWG in the distribution of the poppies and later took over their annual promotion.
You can find buy your own white poppy, or postcards, or just download their free posters and wall charts HERE.