The Electoral Commission has civil sanctioning powers that apply to referendums and elections. More serious criminal matters can and are referred to the police, and then considered by a court of law. The courts already have the power to levy unlimited fines.
It is important to remember that political parties are voluntary organisations, not massive corporates. Disproportionate regulation could discourage volunteering and undermine local democracy.
Political parties and referendum participants of all colours have been fined for breaches of technical reporting requirements – which suggests there is a need to assess whether current timetables and processes are fair, manageable and reasonable.