Labor volunteers have been caught on hidden cameras bragging about using Australian taxpayer funds to work on a US presidential campaign and interfering with Donald Trump and Hillary Clinton campaign signs.

In a video posted online by the conservative undercover campaign group Project Veritas Action, four Australians are recorded saying they received taxpayer funds for flights, accommodation and daily expenses while organising for Democratic senator Bernie Sanders' presidential campaign, a possible breach of US election law.

Former Australian National University Labor Club president Ben Kremer is identified in the video trying to remove campaign signs for Republican candidate Donald Trump in Manchester, New Hampshire, acknowledging in the secret recording that the tactics were not legal.

"F--- you, Donald," he says in the video.