Scottish Water officials have admitted they missed out thousands of customers when issuing warnings about contamination of supplies.

The chief executive of the new authority said customers in Clydebank were being told of the problem with their supplies on Monday afternoon, 48 hours after warnings to other residents.

More than 140,000 people in large tracts of Glasgow have been warned to boil all of their drinking water because of an outbreak of the parasite cryptosporidium.

Authority chief executive John Hargreaves said: "It became clear this morning there was an area we had not contacted customers yesterday and we have done that today."

The parasite can cause vomiting and diarrhoea

Mr Hargreaves said Scottish Water officials had subsequently been in touch with West Dunbartonshire Council over the outbreak's impact on Clydebank.

But the council has complained that it was only able to get details of the instruction to customers to boil their water from Scottish Water's website.

Scottish Water has been forced to defend its handling of the outbreak and has denied it kept people in the dark for more than 24 hours about the discovery of a parasite in supplies.

The authority said its staff had acted "with the utmost caution" not to alarm people living in affected areas of Glasgow.

But the Scottish National Party has demanded answers from the company over the time it took to go public with the information.

A Scottish Water spokeswoman said fears were raised on Friday when high levels of the parasite were found in tests taken from the supply the previous day.

People are being warned to boil their water

GPs in Glasgow were warned on Friday to be on the lookout for a possible increase in the number of patients with problems including stomach cramps, mild flu and diarrhoea.

However, the outbreak was not made public until Saturday, when water bosses realised the parasite levels had increased further.

Cryptosporidium was found in water from the Mugdock Reservoir in Milngavie, East Dunbartonshire.

Those served by the reservoir were warned to boil their tap water before drinking or using it to prepare food, brush teeth or bathe babies.

BBC Scotland was contacted by a Scottish Water emoployee on Monday who expressed concern about the handling of the situation.

The employee, who wished to remain anonymous, said: "The problem seems to be that no-one is very sure about things one way or the other, which doesn't inspire a great deal of confidence. It's quite difficult to know where things are going next.

"There appears to have been confusion about what areas are served by that resevoir - and whether or not you're able to drink that water."

Scottish Water has set up a helpline on 0845 600 88 55. Anyone concerned about their health should contact NHS Scotland on 0800 22 44 88.