Police are braced for a massive and potentially violent rally at Parliament House today and warn it will likely prove the "peak" of anti-vaccine protests engulfing the nation's capital.

New arrivals are joining thousands of interstate protesters already in Canberra ahead of the parliamentary sitting fortnight, a week after demonstrations first erupted.

The Convoy to Canberra targeted the ABC and Government House yesterday, with some protesters mobbing and abusing police officers attempting to intervene.