Parks across the country closed in March and the Government has yet to provide a date for their reopening.
Knowsley Safari Park near Liverpool said it is "critical" it can start selling tickets again soon and Ribby Hall Wildlife centre said "the welfare of animals can not be compromised".
It comes after Chester Zoo bosses said that the attraction is "at risk of extinction" and could end the year £24 million in debt.
The British and Irish Association of Zoos and Aquariums said it has written to the Prime Minister's office to highlight the "worsening financial situation of our members and the urgent need for Government action".
The crisis is set to be debated in Parliament on June 11, after the government announced a grant of up to £100,000 available to zoos and aquariums from May 4.
Neil Trickett, Founder and Director of not-for-profit Wild Discovery Animal Experience at Ribby Hall said: "Animal welfare can not be compromised, but if zoos and wildlife centres are left desperate then that will be the case. Zoological collections should not be allowed to get into these situations and be told that money isn't available to them.
"We are still providing the necessary care to the highest standard for our animals and that won't ever be compromised, but it does make you worry because if the money runs out, what do we do?
"There are so many if's and but's about that scenario and it is worrying because it is getting closer. Time is running out."
Nick made an application for the grant last month, which was rejected, as the government informed him that they felt he had enough money to last through the pandemic.
With outgoings of over £14,000 a month and no visitors through the doors, the wildlife reserve previously introduced a funding page and animal sponsorship scheme to help people support them financially.
"The grant available for zoos is no where near as accessible as everyone was led to believe. We believed it was an opportunity, but I only actually know of one zoo that was successful because the terms of the actual grant are so unrealistic," said Neil.
"I don't know how desperate we are expected to be in in order to be able to get hold of this money to keep caring for our animals."
The burden of social responsibility and the protection of customers meant that most centres across the UK made the decision to close their own doors when other stores and retailers shut down.
Neil claims that the thousands he spent on safety equipment and protective measures has now been wasted, as the centres have been told they still can not open, despite other shopping retailers opening from June 15.
"They have allowed stately home gardens and parks across the country to open, so I do not understand the difference," he said.
"We have all seen pictures of beaches crowded with people who don't take responsibility for their own actions. Yet, as a responsible business we have spent thousands putting safety measures in place since lockdown began, to now be told we can't open. We want to know when we can open our doors because we were fully prepared.
"For a small business, these outgoings and upkeep are a huge financial burden. All we can do now is shout as loud as we can and hope it reaches Downing Street. It's a tough situation, because we can't just shut the doors, go home and be furloughed. We need to keep caring for our animals."
The small zoo homes critically endangered species such as Wildcats and the Phillippine Crocodile and is involved with the biggest animal breeding project in the UK.
Since opening their doors in 2016, the centre also maintains vital project in Uganda, using bee hives as mitigation of human and mammal conflict.
Rachel Scott, marketing director at Knowsley Safari, said that their centre also remaining closed is "really worrying and frustrating".
"We can't understand why it's now OK for people to go into shops or visit public spaces where there's no enforced social distancing, but not stay in their vehicle on the Safari Drive," she said. "It just doesn't make any sense.
"It's critical we're able to start selling tickets again soon to help raise money which will cover running and animal care costs, especially for during the quieter winter months."
A spokesman for the Department for Environment, Food and Rural Affairs (Defra) said in a statement earlier this week: "We understand the challenges faced by zoos and aquariums during these unprecedented times but it's vital that we do not move too quickly in reopening to ensure public health is protected.
"We have provided a £14 million support fund to ensure zoos are able to continue to care for their animals.
"Alongside this, work is ongoing to understand how and when zoos and aquariums may be able to reopen in a safe way to the public whilst maintaining social distancing."