There's nothing quite as comforting as the familiar taste of a cup of tea.

But the recognisable flavour is under threat from climate change, campaigners have warned – meaning the nation’s much-loved cuppa could soon leave a bitter aftertaste.

A report published by aid agency Christian Aid warns that rising temperatures and worsening weather extremes in countries such as Kenya, India and Sri Lanka are having an effect on tea leaves.

It means your regular brew could soon taste harsher with less consistent flavours, they said.

Meanwhile disruptions to harvests caused by the changing climate could also trigger price hikes and unreliable supplies of the staple British drink.

Dr Neha Mittal, senior climate services scientist at the Met Office and visiting scientist at the University of Leeds, said: ‘Tea brands depend on delivering a stable and recognisable flavour profile.

‘As climate variability increases, achieving that consistency becomes more challenging.’

Tea quality depends on a delicate balance of compounds such as catechins, amino acids and polyphenols, which determine flavour and aroma.

Higher temperatures increase the production of more astringent compounds while reducing sweetness, leading to a more bitter taste.

Meanwhile erratic rainfall can dilute compounds that give tea its depth and character.

Extreme weather – including droughts, floods and worsening crop pests - can also put pressure on the plants, leading to lower yields, lower quality and more bitter crops, the report says.

It warned that conditions for optimal growth now sit within a relatively narrow temperature range of between 13°C (55°F) and 30°C (86°F) with adequate but not excessive rainfall.

But these conditions are now breaking down in key tea-growing regions.

‘The result is a simple but unsettling prospect – the familiar taste of the British cuppa, smooth, balanced, reliable, is becoming harder to guarantee,’ the report warns.

Claire Nasike Akello, climate adaptation and resilience lead at Christian Aid, said: ‘For generations, consumers have taken for granted that a cup of tea will taste the same, day in, day out.

‘But that consistency depends on a stable climate, and that stability is now breaking down.

‘What we are seeing is the beginning of a shift towards a harsher brew, with the risk that Britain’s favourite drink becomes more bitter, more expensive and less reliable.’

Reuben Korir, a small-scale tea farmer from Kericho County in Kenya, said that when the weather is very dry or unpredictable, the quality of the tea changes.

‘The leaves are smaller, and we believe the taste is not as good as it used to be during more stable seasons,’ he said. ‘Rains no longer come when expected, and dry periods last longer.’

The UK is also experiencing climate changes that are affecting quality.

Lucy George, who runs Peterston Tea, a small tea farm in South Wales and one of the first commercial tea farms in the UK, said: ‘Seasons are less predictable with warmer winters, sudden late frosts, and irregular rainfall patterns.’

For the farm, warmer periods could accelerate growth, while erratic rainfall or cold snaps could slow growth and affect leaf structure.

‘The balance that gives tea its depth – sugars, amino acids, polyphenols – is closely tied to stable growing conditions,’ she added.

‘When that stability is lost, consistency becomes much harder to achieve.’