De do do do de da da de,,,

"De do do do de da da da" is a satirical song by the British rock band The Police. The song you are thinking of is the similarly named "Di Doo Dah" (written by Serge Gainsbourg) which was indeed released by Jane Birkin (but in 1973, not 1969) on the album of the same name.

The songs are not particularly similar musically, but both revolve around a nonsense phrase used as a stand-in for romantic small talk. Such phrases are called "non-lexical vocables" and are perennially popular in music. The most commonly used syllable in English is "la," although "do"-variants are common in scat, probably because they give a trumpet-like feel to the sound.

https://lightintheattic.net/releases/500-di-doo-dah