John Howells, chief executive at Link, said 'cash use is down by 40 percent – and is still falling,' since the start of the pandemic, which accelerated movement towards contactless payments as people looked to reduce their chance of spreading Covid-19.
But Howells fears cash could be no more in the country in as soon as five years without investment.
He told The Telegraph: "The cost of providing cash infrastructure, which includes the ATMs, security and bulk cash centres is huge at £5bn a year.
"This infrastructure will start to fall apart unless something is done, and we are already seeing ATMs and branches closing at a worrying rate.
"Our cash infrastructure is experiencing death by a thousand cuts."
A recent report by banking trade body UK Finance forecast that one in 20 transactions will be made using cash by 2031, and many young people who live in urban areas might not remember the last time they had a tenner in their wallet.
However, there are estimated to be about five million people - primarily the elderly, those who live in rural areas, and those on lower incomes - who rely on cash.
Howells fears these people could be left behind if more isn't done to help them adapt to digital payments.
He said: "We have 5-10 years to fix digital payments before cash becomes unworkable, and need to start planning how to get the new system working for all."
The issue of money, in whatever form it comes in, is a burning concern for millions of families across the UK amid the cost-of-living crisis.
What's more, the UK is facing the prospect of power blackouts this winter, an energy expert has warned, as he said the Government needed to find more cash to 'help people through this crisis'.
With the price cap now due to rise to £3,549 from October, London Energy Consulting chief executive David Cox said the mechanism was 'not protecting consumers in any way'.
People will 'only get through this winter with the aid of Government money', he insisted – accusing politicians at Westminster of 'glossing over' the problem.
Speaking on The Sunday Show, Cox said: "We're going to be short of gas in Europe for this winter. That will drive prices potentially even higher.
"Not only that, we might be short of gas to the extent that we have blackouts, we don't have enough gas to burn to make electricity, and that is a serious problem the Government are glossing over at the moment."
Boris Johnson has said whoever succeeds him as prime minister will announce 'another huge package of financial support'.
The outgoing PM hinted at the scale of the options to ease the burden being teed up for either Liz Truss or Rishi Sunak to consider, as he insisted 'we must and we will help people through the crisis'.
It comes after Cabinet minister George Eustice said it is 'right' that the next leader waits until they take office to weigh up all the potential moves to combat the cost-of-living crunch.
In an article for Mail+, Johnson acknowledged the next few months will be difficult – 'perhaps very tough' – as 'eye-watering' energy bills take their toll, but he forecast that the UK will emerge 'stronger and more prosperous (on) the other side'.
He said 'colossal sums of taxpayers' money' had already been committed to assisting people with their bills.
But he added: "Next month – whoever takes over from me – the Government will announce another huge package of financial support."
Featured Image Credit: Gordon Scammell / Alamy Stock Photo / CW Images / Alamy Stock Photo
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