Collocations for watchdog - noun

consumer
environmental, financial, health (BrE), industry, media (esp. AmE), nuclear, safety
privacy (esp. AmE)
government, independent, official, public

act as, be

agency, body, group, organization
function, role
site, website
journalism (AmE)
reporters who do the real work of watchdog journalism

watchdog for
an independent watchdog for civil rights

watchdog of
an unofficial watchdog of pesticide use

watchdog on
the government's official watchdog on nature conservation

watchdog over
The committee acts as an independent watchdog over government spending.