They reported that the zoo had been overfeeding giraffes, leaving sloths out in the cold and confining rhinoceroses to “tiny stalls”.
However the zoo described the report as containing “inaccurate presumptions” and “inaccurate clinical assessment”.
In 2013, keeper Sarah McClay, from Glasgow, was mauled to death by a tiger and the zoo was later fined £297,500 for health and safety breaches.
And in 2017 a council report revealed 486 animals had died between December 2013 and September 2016.
The zoo has now been slammed by the wildlife charity over hygiene issues and claims animals were left isolated, cold, and given no time outside.
A damming report published by Born Free claims some rhinos were confined to “tiny stalls” with only enough room to turn around, and not provided with any outdoor space.
It said, despite being a herd species, zebras were separated into individual stalls and shut out overnight - with no bedding or heating.
The charity claimed raw meat was left in a bucket outside the tiger enclosure covered in flies and in full view of visitors, and rats were seen in the raccoon and tortoise enclosures.
A sloth was also reportedly seen “clinging to mesh just inches above the ground to access a heat lamp intended for tortoises”.
The report claimed that “the zoo continues to fail to maintain animals in their natural social groupings.”
A female giraffe was also seen to have “extremely overgrown and curved hooves”, the report stated.
It said giraffes were being fed “inappropriate quantities of carrots” in contrast to natural dietary items such as leaves - with one visitor witnessing 52 guests feeding the animals.
Born Free said there was a “lack of any visible enrichment in enclosures throughout the zoo” and labelled the heat provision as “sub-standard”.
“A number of primates were seen clinging to the mesh to get as close to heat lamps as possible,” they said. “It is our strong view that the zoo continues to fail to meet even basic standards of animal welfare and visitor safety in a number of respects.”
Born Free wrote to Barrow Borough Council to formally highlight their concerns observed during the visit.
A Barrow Borough Council spokeswoman said: “I can confirm that the council received a report from Born Free in regards to the South Lakes Safari Zoo.
“The issues raised in their report are similar to reports recently received directly to the council.
“We take allegations of this nature seriously and will work with the Zoo to address them.
“Any enforcement matters will be reported at a licensing hearing, should that be necessary.”
At a Barrow Borough Council inspection last year inspectors were “impressed” with improvements made since the last visit but added that there was “still much to do”.
Following the council’s most recent inspection, carried out earlier this year, zoo bosses were told to improve the security of enclosures amid fears baboons could escape.
Sam Brewer, of South Lakes Safari Zoo, said: “The report contains inaccurate presumptions and, understandably, inaccurate clinical assessment.
“Cumbria Zoo has, in our last four years, been inspected by over 35 government appointed independent inspectors with the overwhelming outcomes of those inspections being hugely positive, and the continuing process we make here at safari zoo recognised.”
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