The patrol boat came perilously close to heavily-armed warship HMS Somerset and fast patrol boat HMS Sabre, ignoring warnings to stop.
It risked being fired upon after failing to identify itself at Gibraltar while the Navy carried out an anti-terrorist exercise on June 1.
The Foreign Office has made an official complaint to Spain after the latest in a series of confrontations over the sovereignty of the Rock.
SPANISH police boat sparked a security alert off Gibraltar when it sped towards Royal Navy ships on exercise in British waters.
