Water company United Utilities unleashed a monster beneath the sewers of Lancashire in an online April Fools stunt to highlight the perils of flushing inappropriate items down the loo.

The creature, which appears on grainy CCTV footage shot in real sewers, is part of the company's What Not To Flush marketing campaign, which uses school visits, advertising and PR stunts to encourage customers to think before they flush.

The campaign goes by the tagline "What you flush could come back to haunt you."

A total of 64% of Lancastrians admit to having put unsuitable items such as toddler wipes, sanitary towels, cotton buds or nappies down the toilet, while only 13% have a bin in their bathroom to dispose of these items properly.

United Utilities clears 15,000 sewer blockages a year after the wrong items are flushed away. The blockages cause sewage to flood onto roads, pavements, rivers and even into customers' homes.

The monster, which has simian features and a long rat-like tail, can be seen darting through sewer pipes in a series of short eerie video clips. The full sequence of clips can be found at www.unitedutilities.com/monstersightings Rose Francis, United Utilities campaign manager said: "The real monsters lurking in the sewers are the baby wipes, cotton buds and nappies which clog pipes and cause flooding. It's a big issue, as the resulting flooding can cause real distress for households, and pollute local watercourses.

"By using a bin in the bathroom instead of flushing waste, many of these flooding incidents can be avoided. What Not To Flush is designed to highlight the issue in an attention-grabbing and fun way."

According to the Consumer Council for Water, three quarters of all sewer blockages - and half of all cases of sewer flooding - are caused by people putting items they shouldn't down the loo or the sink.

Among the more unsual items found in north west sewers in recent years are a railway sleeper, false teeth, bullets, a motorbike, a wad of used banknotes and a live salamander.