Environmental campaigners have issued renewed calls for a ban on balloon releases after a Powys school released helium balloons into the air to mark it's official opening.

A video posted online showed around 50 balloons were released at the new Clyro Church in Wales Primary School near Hay-On-Wye on Monday, June 11.

Critics of balloon and sky-lantern releases say they litter the environment and cause problems for animals and sealife when they eventually fall to earth, and 16 councils in Wales have already banned the practice.

One county councillor admitted they were "extremely disappointed" at the school's decision to mark it's opening with a balloon release, but said the school had been a victim of misinformation regarding biodegradable materials.

"All balloons are harmful to wildlife and helium is a finite resource but I believe this was planned in good faith, which is hardly surprising given the amount of misinformation regarding biodegradable materials at the moment," said Emily Durrant, Powys County Council's only Green Party councillor.

"Whilst 'biodegradable' can be a big improvement on some plastics, it depends on the type and the method of disposal and processing. It's not a silver bullet. The best way forward is not to produce the waste in the first place, by reducing consumption or changing the way we shop."

Environmental group the Marine Conservation Society(MCS), based in Ross-On-Wye, runs an awareness campaign called "don't let go" encouraging people not to participate in balloon releases.

"We've found through our surveys that balloon rubbish on beaches has increased by 300% over the past few years - you'd hope the message was getting through but clearly it's a problem that's not going away," said Emma Cunningham from MCS.

"The balloon companies have done a terrific marketing job in convincing people that everything's biodegradable but the reality is most sorts of rubber and latex used in balloons will hang around polluting the environment for a minimum of four years, during which time it can affect not just marine environments but also be ingested by cattle and even domestic animals."

According to statistics compiled by MCS, 16 out of 22 councils have a ban on sky lantern or balloon releases, nine of those have a total ban on both.

Powys banned the release of sky lanterns on council-owned or managed land in 2015, but has yet to introduce a ban on releasing balloons.

A statement from the school issued via Powys County Council said: "The Headteacher and chair of the governing body personally ensured that the balloons are biodegradable, as well as the tags that were attached to the balloons."