County education chiefs have warned they face a funding shortfall of £100m to build new and expand existing schools to meet escalating demand for places.

A report setting out the predicted growth in demand for school places in Kent says an additional 12,500 places are needed, meaning the overall number rising from 79,000 to 91,500 between now and 2022.

The lack of places is identified as a key risk for the authority in budget papers issued this week.

Council leader Paul Carter said the authority was “between a rock and a hard place” when it came to finding the money needed.

He said the council would effectively have to take out a mortgage to fund school expansions even though most secondaries were academy schools for which KCC had no responsibility.

He said: “We are between a rock and a hard place on this.

"Most of our secondary schools are now academies yet we are having to pay to meet the need because the [government] grant does not cover the costs.”

He added: “The prospect of borrowing £100m through basically a mortgage over the next 25 years to expand schools that we have no control over is leaving a lot of councils very unhappy.

"The cancellation of free school projects has exacerbated that position. We are pressurising the government to meet the gap between basic need funding and developer contributions.”

The latest version of the council’s school commissioning plan says the equivalent of 82 new forms of entry were needed in the secondary sector between now and 2022, the period the plan covers.

Cllr Roger Gough (Con) cabinet member for children’s services said: “The big increase that has been coming through in primary is now being reflected in secondary places.

"Numbers are continuing in both categories but it is much more marked in secondary.

"Primary rolls will still rise from 123,000 in 2016 to 129,000 in 2020-21. In secondary, you go from 79,000 to 91,500 in the same period.”

“We are between a rock and a hard place on this" - Paul Carter

KCC was facing higher demand because of the government’s free school programme, which had failed to deliver enough new schools and places.

“Delivery has been slow and in some cases has not happened at all. It is the failure of the programme that has put very, very significant pressure on us,” said Cllr Gough.

The funding dilemma is attributed to the fact that the amount the government allocates in grants for each pupil - the so-called basic need - and lower developer contributions, meaning they were not enough to meet the costs of creating more capacity.

While the authority had done well in meeting parental demand and admissions, that was becoming more difficult, he added.

The funding shortfall is identified as being a major risk to the council’s budget next year.

The authority’s corporate risk register says “the expansion required may not be delivered, meaning KCC is not able to provide appropriate school places.”

As a result, “the duty to provide sufficient school places is not met, which may lead to legal action against the council.”

The Commissioning Plan for Education Provision is due to be debated by county councillors at a cross-party watchdog committee today.