From their website (https://www.fosters.co.uk/faqs/, retrieved July 2017, confirmed September 2018)
Q. Is Foster’s suitable for vegans/vegetarians?
A. I’m afraid not.
Company Email (September 2014):
"Fosters [in the UK] is not suitable vegetarians as it is clarified using isinglass finings which are fish derived"
Company email:
"I can confirm Fosters is not suitable for Vegetarians and Vegans."
Also, from the FAQ:
Q. Is Foster's suitable for vegans/vegetarians?
A. I'm afraid not.
Foster's UK
Not Vegan
The one product listed is not vegan friendly.
Products (1)
What the company told us
Correspondence on record, with the date of each entry.