Let us mourn [earth] with a traditional ballad.
- Starts Toxic by Britney Spears *
It’s been over a decade since I watched that episode, but I distinctly recall that it was Tainted Love by Soft Cell
So, according to tardis.fandom.com:
Cassandra plays what she thinks is a “traditional Earth ballad” to mark the destruction of Earth- this song is the racy single “Toxic” by Britney Spears, highly irreverent for the moment.
Rose calls Cassandra “Michael Jackson”, referring to that singer’s well-known cosmetic surgery.
“Tainted Love” by Soft Cell plays after all of the delegates have assembled.