Plastic food pots and trays are often unrecyclable, say councils

Most of the plastic food containers that householders wash out after use and put in the recycling bin cannot actually be recycled, it has emerged.

The mixture of plastics used in many yogurt pots, ready meal trays and other containers limits the ability of councils to recycle them.

The Local Government Association says that only a third can be reused. The rest get sent to landfill.

The plastics industry said it was committed to reducing waste.

The British Plastics Federation said firms needed a financial incentive to choose more recyclable plastics.

The LGA says the government should consider a ban on low-grade plastics.

According to the LGA analysis, around 525,000 tonnes of plastic pots, tubs and trays are used by households in the UK every year, but only 169,000 tonnes of this waste is capable of being recycled.

It blames producers for using a mix of polymers, some of them poor quality.

The LGA, which represents councils in England and Wales, says that some simple tweaks could make a massive difference to this situation.

It points to microwave meals which are often supplied in black plastic material.

However, black is the only colour that can't be easily scanned by recycling machines, meaning that process becomes unnecessarily complicated.

Changing the colour of these items would significantly increase the amount that could be used again.

"It's almost criminal to think that some of the plastics being used are difficult to recycle, and black plastic is almost impossible to recycle," Cllr Peter Fleming from the LGA told BBC News.

"The only reason we have black plastic being used by manufacturers is that it makes the food look good."

When it comes to punnets of fruit and vegetables many are made from up to three different types of plastic, including polystyrene, which can't be recycled.

The LGA wants plastics manufacturers to work with councils to prevent materials that limit recycling entering the system in the first place. It is also calling for government to consider banning low-grade plastics, particularly those for single-use items.

"We need an industry-wide, collaborative approach where together we can reduce the amount of material having an impact on the environment," said Cllr Judith Blake, who is the LGA environment spokesperson.

"But if industry won't help us get there, then the government should step in to help councils ensure we can preserve our environment for generations to come."

As well as calling for a ban, the LGA is looking to the government to make plastics manufacturers pay for the costs of collecting and disposing of plastics that can't be recycled.

"Either they can make the change at the front end so their products are easier to recycle," said Cllr Fleming, "or they can start to help pay for the disposal."

Keith Freegard, from the recycling group at the British Plastics Federation - the leading association for the whole of the plastics industry - said designers often use the colour black for packs to indicate they are a more "top of the range product".

He told BBC Breakfast: "Unfortunately those designers didn't realise that when those packs arrived in the recycling factory after it had been separated by consumers, the black dye is not able to be seen by the sorting scanners in the recycling plant - so that does need to change."

He said the industry was already trying to find ways to use more recyclable packaging.

But he added: "At the moment there's no fiscal or monetary system in the UK that makes designers go for the really good-to-recycle designs and those who make packs which are less easy to recycle, they should be paying more money into the system."

The LGA report comes hot on the heels of a study from the National Audit Office that suggests that half the packaging reported as recycled is actually being sent abroad to be processed.