According to a few different news sources (including The Mirror newspaper, Now Magazine and The Star newspaper) at a recent 21st birthday party.  The music at the party was provided by musician/producer Mark Ronson who, according to the Mirror newspaper, "joined a supergroup, including Jamiroquai's band and DJs from Hed Kandi, and had the whole place rocking".

Now, we know ex-Jamiroquai bass player Stuart Zender works with Mark Ronson so perhaps that is the definition of "Jamiroquai's band"...