A British wildlife conservation group on Friday said it had uncovered thousands of breaches of animal welfare standards at zoos across Europe, urging improvements.
The Aspinall Foundation claimed it had found more than 3,000 breaches of standards set by the European Association of Zoos and Aquaria (EAZA) at 29 zoos over 18 months.
The EAZA aims to ensure its member zoos and aquariums "maintain the highest standards of care and population management", according to its website.
The association had 308 full members as of October last year, including dozens in the UK.
The probe, which took place across 12 European countries including the UK, claimed that the EAZA failed to ensure compliance, leading to animals "mentally and physically suffering".
In the 29 zoos visited, researchers said they saw elephants locked outside their shelters in cold temperatures, bears housed in concrete enclosures with no shelter, and one hippo with no access to a pool.
Elephants had the highest number of accommodation issues in the zoos, followed by rhinos, lions, tigers and giraffes, the Aspinall Foundation alleged.
Its report accused the EAZA of shortfalls, including the absence of unannounced inspections, and said its dependency on membership fees cast doubt on the rigour of its enforcement.
The EAZA denied that membership fees influenced its screenings, adding that fees were standard practice in professional associations.
Member zoos allegedly maintained their accredited status despite breaches linked to enclosure furnishings, animal shelter, and exercise space,
A "significant flaw" was a gap of seven to 10 years between accreditation and renewal, which the report said "may result in a decline in standards".
The report also raised "serious concerns" about the trust placed in EAZA accreditation by the public and zoos.
Damian Aspinall, chairman of the Aspinall Foundation, condemned the accused zoos for creating a "myth of conservation" and said the EAZA was a "pointless organisation unless it's effective and honest with the public".
EAZA executive director Myfanwy Griffith said in response that the report failed to "truthfully represent the aims and effectiveness of EAZA's accreditation programme".