Scientists have found "disturbing" problems in more than a third of foods sampled in lab tests, it was reported today.

The results of 900 sample tests by councils in West Yorkshire found 38 per cent of foods were mislabelled or not what they claimed to be, according to a national newspaper.

It reported that problems included mozzarella that was less than 50 per cent cheese, ham on pizzas found to be made from poultry or "meat emulsion" and prawns that were 50 per cent water.

It also said that some beef mince was found to contain pork and poultry, while a herbal "slimming" tea was found to be neither herbal or contain tea, instead containing high levels of a prescription slimming drug.

West Yorkshire's public analyst, Dr Duncan Campbell, told the paper: "We are routinely finding problems with more than a third of samples, which is disturbing at a time when the budget for food standards inspection and analysis is being cut."

According to consumer group Which? The number of food samples taken to test whether they were what they claimed to be fell almost seven per cent between 2012 and 2013, after falling 18 per cent the previous year.

It said about ten per cent of local authorities did no sampling of this kind at all last year.

Richard Lloyd, the executive director of Which?, said tougher penalties and more testing was needed.

"No one wants to see another incident like the horsemeat scandal happen again and the rigorous enforcement of standards underpinned by effective levels of food testing is essential for restoring consumers' trust in this industry," he told the paper.

The paper reported that the tests, carried out at a public laboratory, also found a third of fruit juices were mislabelled or did not contain what they said they did.

Two contained additives banned in the EU which have been linked to behavioural problems in tests on rats.

There was also a problem with counterfeit vodka made using antifreeze.

Dr Campbell told the BBC's Today programme today that officials were seeing "perhaps more serious breaches of the law laid on top of a rumbling amount of fairly minor problems".

He added: "In the areas where local authorities are doing little or no routine sampling, problems such as the ones we are finding are not being discovered.

"A lot of food in the UK is distributed nationally but there is still a fair proportion where it is produced and sold locally and it is only by having local enforcement officers on the ground visiting those premises that those problems will be picked up.

"Also I'm sure there is a deterrent effect. If a business is perhaps under pressure and thinking of cutting corners and it's aware that it's not likely to have an inspection, it's perhaps more likely to cut corners and substitute cheaper ingredients for more expensive ones and so on."