The pressure group for lower taxes, government transparency and an end to wasteful government spending says that at the long-term average rate of growth in NHS spending and the forecast rate of GDP growth, NHS spending is estimated to reach £2.6tn in 2099-2100, which would be 24.6% of UK GDP, at £10.5tn.

NHS spending in 2024-25 was £187bn, equal to 7% of GDP, with spending set to grow by 3% per year during this parliament. As a result of this, NHS spending will make up half of all day-to-day government spending by the end of the parliament, according to the Resolution Foundation.

However, this rate of spending growth is below both the long-term average rate of 3.6%, and the rate of real terms funding growth called for by the BMA in their submission to the autumn budget, when they called for real terms funding growth of 6.7% for the DHSC as a whole. If NHS spending returned to the long-term average rate after this Parliament, and assuming the average rate of growth forecast by the OBR up until 2073-74 remains consistent, the NHS will be equal to a quarter of UK GDP in 2099-2100.

If the growth rate was increased to 3.8% - the average rate of growth since the 1980s - as called for by some campaigners, the NHS would be equal to a quarter of GDP seven years earlier, in 2092-93. According to the Health Foundation, this rate of growth is necessary to achieve ‘sustained improvement'.

Shimeon Lee, policy analyst of the TaxPayers' Alliance, said: ‘Brits often joke that the UK is a health service with a country attached, but it may not be long until this joke turns into a reality.

‘If NHS funding increases return to the long-term trend, as many are calling for, it will be equal to a shocking quarter of the economy by the end of this century.

‘As well as demonstrating the need for spending restraint and productivity increases, this is also a reminder of the urgent need to boost growth.'