School funding suggestions delivered to the Chancellor by scores of Cumbrian headteachers and senior education figures are being "examined", it has been revealed.

Liz Truss, the Chief Secretary to the Treasury, has replied to an open letter sent to Philip Hammond last month by the Cumbrian branch of the National Association of Head Teachers union.

The letter was signed by more than 70 headteachers, governors, business managers and other senior education figures.

It urged the Chancellor to take action to ease the financial squeeze on school funding.

They say they find the current situation "untenable" - with fears that children will suffer - and that existing shortfalls are "causing tensions" between Cumbria's cash-strapped large secondary and primary schools and small, rural schools in many local communities.

The letter was sent as a campaign for improved school funding gathers pace ahead of the Chancellor's Autumn Budget on November 22.

Mrs Truss sent a reply this week, received by the Cumbrian branch of the National Association of Head Teachers.

It states: "My officials are examining your ideas and suggestions. Whilst it would not be appropriate to respond in detail to the points you make at this stage, I can assure you that your suggestions have been noted."

Campaigners say that latest figures show Cumbria's schools will face a shortfall of £13.3m by 2020 - the equivalent to a loss of £226 per pupil or the salaries of 272 teachers.

The figure had been £23m before the impact of a new National Funding Formula (NFF) and other changes were evaluated.

The majority of Cumbria's schools are forecast to receive an increase to their basic, per-pupil income under the new NFF due to be implemented in 2018-19.

Campaigners say the revised formula is welcome and helps tackle a "historic underfunding" of the county's schools yet it fails to take into account rising costs that is leaving many facing cutbacks to balance the books.

Cumbrian schools set to receive a reduction in their basic, per-pupil income under the new NFF are asked to contact the NAHT branch to discuss how the impact it may have.

The union has pledged to continue its campaign to ensure that no school is adversely affected by funding changes or rising costs.

The branch believes more should be done to ensure that children and schools eligible for extra support through Pupil Premium funding receive the additional funding they are entitled to.

Clem Coady, president of the Cumbria NAHT, said: "The NAHT have repeatedly stated our support for a fairer redistribution of funding.

"However, the National Funding Formula is being implemented at a time when schools are facing severe financial pressures.

"The National Audit Office already recognise that £3 bn is needed by 2019-20 to maintain current levels of education. Therefore £1.3bn, while a welcome improvement on previous announcements, still falls significantly short of this figure.

"The Public Accounts Committee further warn ministers that education funding is currently at a similar rate as the 1990’s. When you compare funding spent on education as a percentage of GDP, we are currently spending less on education than the government of the early 1980s."

He added: "The additional income being quoted for some schools locally is a welcome redistribution, particularly since historically, Cumbria has been comparatively underfunded.

"Any additional income will go some way to addressing the numerous increased cost pressures on schools. However, when all the costs are factored in, this will still not be enough for many of Cumbria’s schools, with several already having to consider making drastic cuts to staffing and services to balance the books."

Union officials are also set to holding meetings soon with Penrith and the Border MP Rory Stewart; his Copeland counterpart Trudy Harrison, who sits on the influential Education Select Committee; and South Lakes MP Tim Farron to discuss funding issues.