People who are looking to undergo tooth whitening have been told to ensure they visit a fully-licensed practitioner.

This warning comes after the New Zealand Ministry of Health launched an investigation into unregistered firms that are carrying out the procedure down under, TV NZ reports.

The decision to look into the existence of bogus or "cowboy" companies comes after a woman suffered burning gums, which had also turned partially white, after she visited an unlicensed establishment.

However, the person in question escaped punishment because they were not official health professionals, which has led to increased calls for the industry to be more tightly regulated.

The country's Environmental Risk Authority has discussed the possibility of banning the use of hydrogen peroxide that is stronger than 3.6 per cent by unregistered practitioners.

Meanwhile, a dentist in Bristol has warned those who are seeking teeth whitening services to avoid bogus firms, after an apparent surge in the number of unknown companies offering discount rates in the UK.