The northwest’s biggest ever fatberg has been discovered lurking underground in a Liverpool sewer.

The 84-metre mass is longer than a passenger plane and weighs 90 tonnes – around the same as 13 African elephants.

Engineers used pick axes to dig out the blockage of congealed cooking fats, grease, wet wipes and sanitary products which have been poured down the sink or flushed down the toilet.

United Utilities, which made the discovery five metres below ground, said it could take eight weeks to fully remove the fatberg, which will then be sent for recycling into biofuel.

A spokesperson for the water company said: “Our sewer systems are only designed for water, toilet paper and human waste to flow through and not the increasing volume of fat and other items such as wet wipes which are contributing to over 25,000 sewer blockages in the northwest every year.

UK fatbergs in pictures Show all 7 1 /7 UK fatbergs in pictures UK fatbergs in pictures Sidmouth's 'monster' fatberg The blockage is 64m long AP UK fatbergs in pictures 64m fatberg in Devon This photo was released by South West Water AP UK fatbergs in pictures Workers tackle fatberg A fatberg is a mass of hardened fat, oil and baby wipes AP UK fatbergs in pictures On display A part of the Whitechapel fatberg on display in the Museum of London Museum of London UK fatbergs in pictures 130-tonne Whitechapel fatberg Authorities are tackling a huge fat blockage in the capital’s sewage system PA UK fatbergs in pictures Fatbergs by the numbers Data compiled by statistics agency Statista UK fatbergs in pictures Clogged mass A fatberg beneath Whitehall Thames Water

“Fatbergs block our sewerage system which can wreak havoc in homes and businesses.

“These blockages stop sewage passing through the pipe, eventually forcing the wretched smelly gunk back up to escape wherever it can onto roads, gardens and homes.”

The northwest's biggest ever fatberg measuring 84 metres long and weighing 90 tonnes has been discovered in a sewer in Liverpool. (United Utilities)

Millions of pounds are spent cleaning drains and sewers across the UK because of items that shouldn't be in them.

Wet wipes, cotton wool, nappies, cotton buds and dental floss are just some of the culprits.

United Utilities said we can all do our bit to banish fatbergs by following some simple rules: