A Mayhew Animal Home volunteer says she is "disgusted" at what is going on inside the Kensal Green charity as bosses consult on restructuring plans.
Judy Stapleton has volunteered at the charity in Trenmar Gardens for seven years and said she is "horrified" by what is happening.
Mayhew is currently in a consultation period with its employees in relation to a proposed restructure.
Mayhew trustees have also been contacted by the British Veterinary Union (BVU) in Unite urging them "not to make hasty decisions to cut jobs" following the redundancy of two Registered Veterinary Nurses (RVNs).
Judy said: "I'm absolutely disgusted by what's happening. I understand the charity might be short of money, but I don't understand why there's no communication between the management and the staff.
"Long standing, highly professional and dedicated staff are being made redundant.
"Animal welfare posts are disappearing, the head of kennels is being made redundant, the post involved with rehoming dogs is redundant, so who is going to look after the cats and dogs in need? Who will be available continue the outreach work and the work in the community with the homeless?
"The buck has to stop with the board of trustees and the interim CEO."
Howard Bridges joined the charity in March as interim chief executive while Julianne Hicks, chair of the board has been in post just over a year.
"They have both decided that the Mayhew needs a total reorganisation", Judy added.
Former chief executive Caroline Yates remains with the charity as head of international projects and relations.
Mayhew's patron is the Meghan Markle, Duchess of Sussex, who wrote in the charity's 2020 Annual Review: "I want to thank every animal lover across London, the UK and the world who has supported Mayhew during the past year.
"Your help has meant that, despite the hardship, Mayhew has been able to continue providing vital support to cats and dogs, and the communities around them."
Celebrity supporters include Louis Theroux and Sir Tony Robinson.
"Because of the shortage of staff, the Mayhew can only look after a maximum of five dogs when it has the capacity for 15," added Judy.
"The charity can home about 70 cats but their numbers are being reduced, again because of staff shortages.
"All the work the previous CEO did to make the Mayhew into a wonderful community asset for rehoming animals and educating pet owners is being thrown away."
Judy said she heard "talk" that volunteers will be able to take over the work of full time fully trained staff, but she said she didn't have that "knowledge or experience" despite undertaking several City & Guild courses at her own expense.
"Permanent staff get to know the animals in their care. As a volunteer I see the animals once a week so cannot possibly have the same relationship with them as the person handling them on a daily basis.
"With only one full time staff member on duty at a time to look after these animals it is likely that volunteers will be asked to work with unassessed animals.
"Animals are already being left for long hours during evening and nights because there are insufficient staff to take care of them properly. It's heartbreaking.
"This home use to pride itself in caring for unwanted animals and working with the community.
In an open letter to Trustees Suzanna Hudson-Cooke, veterinary surgeon and branch chair of BVS wrote: "We note with concern that two RVNs have already been made redundant, the only redundancies thus far from the clinical team, and wish to impress upon you just how vital RVNs are to the veterinary team.
"Vets cannot do their job without RVNs to support them, and these job losses will place additional strain on day to day operations.
"The workers of the Mayhew will have our support in seeking union recognition, seeking job protections, and seeking reassurance from yourselves as to the future of the charity."
Mayhew supporter Carmen Ramos said: "It's shocking that changes are being implemented by those with little knowledge of how a small animal rescue works.
"Mayhew has stood proud for 140 years, takes only one to break it."
A spokesperson for Mayhew said the pandemic had "impacted our finances and the services we offer" and that a "small number" of staff would be made redundant.
Changes did "not affect welfare officers or staff members that work in the cattery".
They added: "Over the past year, Mayhew’s kennels have been quieter due to the booming demand on pet rehoming which has coincided with us having less staff on-site due to the pandemic, social distancing and through colleagues isolating for safety."
They said the charity was undergoing a restructure "in order to future proof our organisation and ensure our services can continue long-term for our beneficiaries."
"Like many charities, we are having to take some difficult decisions on how we operate due to financial issues.
"Going forward, we believe that hard decision we are making now will help us meet the needs of our beneficiaries in the future."
They said they were still committed to their international work in Afghanistan and Georgia but that it "does not take precedence over our local operation."
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