According to the report, around 70% of first-time buyers took out a mortgage with an initial term of more than 25 years in 2020, up from 45% in 2010.

This mortgage agreement can add significant costs over the longer term. Nationwide calculates that increasing a mortgage term from 25 years to 35 years can increase the total amount of interest paid on a typical mortgage by 40%

The building society added that higher house prices relative to earnings continue to make raising a deposit a significant barrier for first-time buyers.

It said that, across the UK, a 20% home deposit now typically equates to 104% of the pre-tax income of a typical full-time employee, up from 87% ten years ago. However, low mortgage rates have kept monthly payments relatively affordable.

Andrew Harvey, senior economist at Nationwide, said: “In 2018-19, around 40% of first-time buyers had some help raising a deposit, either in the form of a gift or loan from family or a friend or through inheritance. This is up from around a quarter in the mid 1990s.”

“The good news is that for those that are able to raise a deposit, the cost of the typical monthly mortgage payment relative to take-home pay has been trending down in recent years.”

The index also studied the cost of house prices in relation to average annual earnings. Mr Harvey said: “At the end of 2020, the UK first-time buyer house price-to-earnings ratio stood at 5.2, close to 2007’s record high of 5.4, and well above the long-run average of 3.7.

“We have also seen a significant widening in the gap between the least affordable and most affordable regions.

“London has been the least affordable region for most of the past 40 years – the house price-to-earnings ratio in the capital reached a record high in 2016 of 10.2 and remained elevated at 9.2 at the end of 2020. Scotland currently has the lowest house price-toearnings ratio at 3.2, closely followed by the North (of England) at 3.3.

“Looking over the longer term, northern England and Scotland have historically seen lower house price ratio ratios than southern England, Wales and Northern Ireland.”

Nationwide’s index also found that housing affordability is particularly challenging for people working in jobs such as construction and manufacturing, as well as for cleaners, couriers, and those in the care and leisure sectors, and other personal service jobs.

The report found that within these groups, typical mortgage payments would represent more than 40% of average take-home pay.

Nationwide’s most recent house price figures, for December, showed annual house price growth reached a six year high of 7.3%. House prices ended 2020 some 5.3% above the level prevailing in March, when lockdown hit the UK.