Costumes for Elizabeth were designed by Alexandra Byrne. This particular costume, however, did not make the final cut of the film. It can be seen in a black and white behind the scene photo, and was on display for a time as well (where you can see the true colour of the piece).
The gown was used again in The Tudors on Natalie Dormer, where a front piece was added to disguise the fact that the costume did not fit.
The base of the gown seems to have been utilized without the gold jacket for a small film version of the reign of Mary, Queen of Scots.
Interestinly, the fabric used in this dress wound up being used in another costume here.