Image copyright Getty Images Image caption Many parents carry wipes for convenient cleaning

All wet wipes sold as "flushable" in the UK have so far failed the water industry's disintegration tests, the BBC has found.

Water companies say wet wipes don't break down and are causing blockages which cost millions to put right.

Manufacturers insist their test is adequate and say sewer blockages are caused by people putting non-flushable wipes down the toilet.

Wet wipes are sold for everything from make-up removal to surface cleaning.

Most importantly when it comes to flushability, they're available as moist toilet tissue.

The government has said it is working with manufacturers and water companies to develop a product that does not contain plastic and can be safely flushed.

Media playback is unsupported on your device Media caption How to break your wet-wipe addiction

The sticking point comes over what you count as "flushable".

Wet wipes will flush - in that they will disappear down the U-bend of your toilet. The problem is what happens to them next.

Wet wipes are behind up to 80% of blockages in UK sewers, a key element of the infamous giant obstacles known as fatbergs, according to water companies.

They say it costs £100m a year to deal with them.

Skips full of wipes are caught by the filters at water treatment works and end up in landfill.

From their treatment sites across the North West, United Utilities collect around 12,000 tonnes of wipes and other rubbish every year.

Image caption Wet wipes causing a blockage at a house on the outskirts of Manchester

Tony Griffiths, from United Utilities, said: "It's extremely frustrating. The amount of money that gets spent on dealing with blockages and disposing of this material could be reinvested in our ageing infrastructure."

He added: "If we're not spending all this money, we could actually work to reduce customer bills."

Some in the water industry are losing patience.

Matt Wheeldon, a director at Wessex Water, has been pushing for action to prevent wipes being labelled as flushable.

He said: "I think they're a complete scourge on our society.

"Whoever came up with the bad idea didn't think about the impact they're going to have on the environment."

He added that it was "technically illegal to put anything down the toilet that's going to block up the sewer".

"Despite what the label says, these wipes definitely shouldn't be flushed down the toilet," agrees Natalie Fee, founder of campaign organisation City to Sea.

She points out that most manufacturers specify that so-called flushable wipes should only be flushed "one at a time".

"Manufacturers clearly know this is a problem. We need to start seeing them change what they say [on the packaging]. It can be confusing for consumers," she told BBC News.

Deadly consequences

Meanwhile, wipes which escape the filters have an even greater environmental impact, ending up in rivers and on beaches.

The wipes contain tiny plastic fibres which go on to harm fish and other marine life as the fibres are released and ingested, sometimes with deadly consequences.

In addition, the plastic fibres might then go on to be consumed by other animals potentially entering the human food chain.

Media playback is unsupported on your device Media caption Wet wipes clogging up London sewers

Thames21 is an environmental charity which organises clear-ups of wet wipes from the banks of the Thames.

In the first six months of 2018, volunteers picked up around 120,000 wet wipes from one stretch of the riverbank near Hammersmith Bridge.

AJ McConville, from the charity, said: "The wet wipes are changing the shape of the foreshore.

"What seems to be happening is that wet wipes are getting snagged on something, and then they will slow down the water around them by creating turbulence, and by doing that they therefore attract even more wet wipes and more sediment to accumulate around them."

Image caption Wet wipes on the riverbed of the Thames at low tide

Manufacturers have made efforts to improve the packaging of non-flushable wipes, making the "do not flush" logo larger and more prominent.

But it is the wipes marked "flushable" where there is disagreement.

Scientists at WRC, a water-testing laboratory in Swindon, carry out tests on wet wipes to assess their ability to disintegrate when they are flushed into the sewers.

They put wipes into conical flasks full of water and rotate them on a shaking platform - which they believe mimics the turbulence of water conditions in a sewer.

Using this technique, they have found that none of the wipes marked "flushable" which are currently available for sale in the UK pass the test.

There is hope on the horizon though. They also test new products still in development, and have found some wipes which do break down - but none of these are yet available on the UK market.

The manufacturers use a different test. It is more vigorous, and means that wipes break up more quickly.

Some water industry experts likened this to putting the wipes in a washing machine, and said it didn't realistically reflect what happened in the sewers.

Image caption There are many brands of wet wipes available, but only some of them are marketed as 'flushable'

But the manufacturers insisted their test was adequate, and believed that wipes marked "flushable" weren't the problem.

Last year, the government asked the manufacturers and water companies to agree a flushable standard.

But these efforts have failed, leaving the water companies to insist that only three 'Ps' should go down the toilet: pee, poo and paper.

Hear more on Costing The Earth on BBC Radio 4 on 13 November at 15:30 BST, repeated on 14 November at 21:00.