That is because its analysis found that the cost of delivering a new home has risen by 17%, while prices have only increased 1%  since 2022. 

The property portal says that 64% homes in southern England have average sales prices at levels that can support the cost of delivering new homes, compared to just 13%in the Midlands and 10% in the North.

The findings show the scale of the challenge facing the government in order for it to achieve its target of building 1.5m homes over five years.

Zoopla’s calculations come from analysis of reports and accounts from the large listed housebuilders, which shows how their delivery costs have accelerated much faster than selling prices.

Smaller homebuilders, which account for 30% of new build developments in England, are likely to have experienced even higher inflation, Zoopla says.

Higher borrowing costs, building materials and labour, as well as increased costs relating to policy changes have all made the delivery of homes more expensive.

Additional increases are in the pipeline due to the Building Safety Levy and Future Homes Fund, it says.

At the same time, demand for new homes has weakened following the end of Help to Buy and higher mortgage rates.

Demand from housing associations, which buy homes through Section 106 agreements, has also reduced due issues such as building safety costs and higher borrowing rates.

Even though the viability to develop new homes is stronger in southern England, it has some of the most unaffordable markets for home buyers. This limits demand, creating risk and slow sales rates for developers.

Zoopla proposes four key areas of change to help address these problems:

• Planning Reform: Continue to simplify and unlock the planning process to make it easier to develop land
• Regulatory Review: Re-evaluate new policy burdens that increase development costs
• Targeted Funding: Deploy new funding for affordable housing quickly and strategically to enable housing associations to acquire new homes
• Demand Support: Consider a return of targeted support for first-time buyers to boost demand without inflating prices across the board

Zoopla executive director Richard Donnell says: “While the government says it wants to ‘build baby build’, our analysis shows that this can only be currently achieved across half the country, in areas that are typically more expensive for consumers to buy.

“It is much harder for builders to build homes where it’s affordable for home buyers to buy.”

“The government can’t control the price of raw materials like bricks or concrete, but it can influence the rising costs of new regulations.

“While recent planning reforms and affordable housing funding are positive steps, they are not a complete solution to boosting new home building.

“Further reforms are needed to boost capacity and speed at the local planning level and new funding should be focused on immediate, not long-term, delivery.

“Direct support for homebuyers could help, but if deployed, requires careful targeting.”

Donnell adds: “Builders also need to ensure they are marketing homes as efficiently as possible.

“Affordability pressures are making people look further for their next home, especially in the new homes market.

“Building more homes is vital in helping to ease the pressures facing those in the housing market, but the viability of building is at risk from further cost increases and we can’t rely on higher house prices to fix it.”