The county’s largest local authority is sitting on a £105 million pot of unspent cash earmarked for services such as schools.

The underspend figure for struggling Kent County Council (KCC) relates to money given to it by developers as part of planning deals.

Using Freedom of Information legislation, the Home Builders’ Federation (HBF) discovered councils across the country had banked £8 billion, via section 106 (S106) contributions, earmarked for projects such as affordable housing and roads.

Conservative-run KCC was urged by Labour to “come clean” and the Liberal Democrats suggested it was symptomatic of the “housing crisis” in Kent.

KCC claimed the figure is relatively small given the population of the county (1.8 million) and the £105 million underspend relates to 12 districts and boroughs.

The council is having to make tens of millions of pounds of savings in order to balance the books or face going bust.

But the HBF said S106 contributions are supposed to benefit communities.

The trade body added: “This research, however, demonstrates that a lack of capacity or willingness to spend developer contributions by some local authorities is preventing communities across the country from realising the benefits that have been paid for by the industry.

“This, in turn, has inevitable consequences for communities’ perceptions of development and the wider narrative around and perception of house builders.”

The HBF table of 20 underspending councils for developer contributions is topped by Oxford County Council (£287.5 million), followed by Tower Hamlets (£166.8 million) with KCC in seventh place.

Margate KCC member Cllr Barry Lewis said: “The county council has to come clean about what they have not spent on infrastructure promised to the residents. People’s lifestyles will continue to be impacted while this lack of transparency is allowed to exist.”

Liberal Democrat colleague at County Hall, Cllr Richard Streatfeild said: “There is a housing crisis in Kent - a crisis in social, affordable and right size housing.

“I would like to see a detailed breakdown of what money is attached to which housing development, especially in places like Maidstone. There needs to be greater transparency.

“But we have to be honest - the HBF is a trade body for the house building industry and is trying to get the government to make its life easier.

“There doesn’t need to be a change of the law, there needs to be a change of political will. There is a crisis and it’s got to be solved.”

Cllr Derek Murphy, KCC cabinet member for economic development, said: “We always strive to use developer contributions to ensure that we put in the right infrastructure at the right time, in line with central government policy, and delivering the best outcomes for the residents of Kent.

“The unspent developer contributions should be viewed in the context of the size and scale of KCC as a local authority area, having the largest population in the UK.

“It’s also important to note that most projects we deliver require a significant amount of upfront capital, and these sums are spread across all 12 districts and boroughs in Kent.

“Adding further context, the cost of building a two-form entry primary school is currently in the region of £10m, which illustrates the total figure of unspent contributions is relatively low, given the rate of developments in the county.

“The delivery of these infrastructure projects can also be influenced by a number of other factors, specifically that large developments often take many years to complete, and the contributions not only reach KCC gradually, but come in from a number of different development companies.”

The Local Government Association (LGA) said delays to the use of S106 monies can arise from the complexity of certain developments while affordable housing can take time finding sites or obtaining planning permission.