A generation of school buildings have leaking roofs, poor windows and cold cramped classrooms, a head teacher has said, blaming the Welsh government.

Jon Wilson said he has asked for 13 years for "deplorable" buildings at his own school in Newport to be revamped.

The Welsh government said it was spending nearly £2bn on the most "ambitious" investment to upgrade schools and colleges since the 1960s.

But teaching union leaders have claimed not enough money is being spent.

Mr Wilson, from Duffryn High School, said the Welsh government's investment under the 21st Century Schools programme "hasn't worked" for the school.

He claimed it has been poorly executed across the country.

It comes as plans for a new Welsh-medium secondary school on the Duffryn High School site are set to be resubmitted to Newport council.

"I think there's a whole generation of schools and education out there that are very very close to that picture," Mr Wilson said.

Media playback is unsupported on your device Media caption The school's English teacher Lauren Sharpe describes some of the problems

"Like many things in Wales, [21st Century Schools programme] good in concept, relatively poor in execution; just not enough of it going on to produce the facilities that our children deserve."

He added: "I've been to see some fabulous new schools around Wales, but there's all too few of them.

"I think the reality is closer to where we are with our deplorable buildings, than to the very, very small number of new schools."

Dr Philip Dixon, Wales director of the Association of Teachers and Lecturers, said the situation in Duffryn was "not unique", claiming there were conditions around Wales that "the Victorians would be appalled with".

Speaking to BBC Radio Wales, he said the Welsh government had "chronically underspent" in the early years of devolution, and now "the chickens are coming home to roost".

Dr Dixon called on the Welsh government and local authorities to stop playing "ping pong" over who is to blame, saying that the original £1.4bn budget of the 21st Century Schools programme needed to be doubled.

Owen Hathway, Wales policy officer for the National Union of Teachers, said school buildings were in "dire need of an overhaul" with poor conditions having a "profound impact" on standards.

Plaid Cymru leader Leanne Wood said it was wrong children were "forced to endure almost Dickensian conditions in their seats of learning".

She said her party's plan for a National Infrastructure Commission would "transform" the nation's schools, hospitals, roads and railways by spending the money needed to upgrade them.

'Ambitious investment'

Duffryn High was due to be upgraded as part of a deal that would have seen a new Welsh medium school share the site, but the plan was rejected over fears it may flood.

The school has had to abandon two classrooms because of cold and damp.

Newport council has admitted "urgent" work is required but cuts have made it difficult for it to be carried out.

A Welsh government spokesman said almost £2bn would be spent on school and college buildings between 2014 and 2024, including £28m on schools in Newport.

"Our commitment to learners is also reflected in education spending; which is 4% higher per head in Wales than in England, a country where their 'Building Schools for the Future' programme was cut in 2010," he added.