A “fatberg” weighing an estimated 100 tonnes has been discovered blocking sewers in east London, officials have said.

The mass of congealed fats, oils and grease measures about 100 metres long (328ft) and weighs about a third more than the heaviest of the British army’s battle tanks. It has been called the grandchild of the 2017 Whitechapel fatberg, which weighed 130 tonnes and stretched for more than 250 metres (820ft).

“This latest fatberg shows exactly what happens when fats, oils and wipes go down our drains – they don’t disappear, they build up and cause serious damage,” said Tim Davies, the head of waste operations for north London at Thames Water.

“The cost of clearing blockages and repairing sewers runs into tens of millions of pounds every year, and that money ultimately comes from our customers.”

The latest fatberg, which has been found in the Whitechapel area of the capital, has led Thames Water to urge people to think carefully about what they pour down sinks and flush over the festive period.

The company reports a seasonal rise in the number of blockages during December and January, and says clearance costs reach £2.1m over the period. It has urged people to scrape food scraps from any dirty dishes, ensure plugholes are fitted with a strainer and avoid pouring liquid foods down the sink, such as gravy or cream.

The 2017 fatberg was among the largest discovered in the capital. A sample even went on display in the Museum of London after it was broken up by workers.

Speaking at the time, Thames Water’s head of waste networks, Matt Rimmer, said: “It’s basically like trying to break up concrete. It’s frustrating as these situations are totally avoidable and caused by fat, oil and grease being washed down sinks and wipes flushed down the loo.”