About 340,000 tests were carried out on tap water across the region and just over 600 failed to meet national and European standards.

Independent watchdog, the Drinking Water Inspectorate (DWI), carried out the annual survey.

They say United Utilities must remain committed to improving standards further to maintain the quality.

There is no doubt the quality of drinking water across the country is the highest it has ever been, says the watchdog, but the North West does fall below the national average.

About one sample in every 550 failed to meet national and EU standards.

DWI inspector for the region, Claire Jackson, says major investment by United Utilities has improved the quality of water but more needs to be done, particularly to ensure households do not receive discoloured water.

The legal standards for drinking water were set out by the government in the Water Quality Regulations.

The standards include how much bacteria, chemicals and metals are present, the way water looks and how it tastes.