put/stick two fingers up at somebody
put two fingers up at (someone or something)
1. Literally, to raise one's index and middle finger up at someone, with one's hand turned outward (a rude gesture of disrespect in the UK). Primarily heard in UK. It's not uncommon to see young kids putting two fingers up at police in this part of town.
2. By extension, to demonstrate one's disrespect, dislike, or anger towards someone. Primarily heard in UK. Voters have essentially put two fingers up at the political establishment by voting for populist candidates from across the country.