A total of 3.2 million households in the UK have acquired a pet since the start of the pandemic, according to the Pet Food Manufacturers' Association.
That means the country now has 17 million pet-owning homes, the association says.
Young people are the main drivers of this trend, with more than half of new owners aged 16 to 34, the PFMA says.
Many have bought pets in response to social isolation, but there are concerns about animal welfare, it adds.
"Introducing a pet to a household in Covid times can have repercussions or create some unexpected difficulties," said the association's deputy chief executive, Nicole Paley.
UK supermarkets have already noted an "unprecedented" rise in pet ownership and have warned that it is causing a shortage of some dog and cat food products.
Helen Warren-Piper, general manager of Mars Petcare UK, which makes Pedigree and Whiskas, said: "We recognise retailers are experiencing unusual demand for pet food during lockdown."
Under-35s account for 59% of new pet owners, while 56% of those buying a pet for the first time have children at home, the PFMA says.
But some are finding that their new acquisition is more trouble to look after than they had anticipated.
More than a third of new owners said it was like having a baby, while about a fifth of families with children said training their new pet was proving challenging.
As a result, 5% of those who had bought a pet during the pandemic had already given it up.
On the positive side, 74% said their pet had helped their mental health while they were coping with coronavirus curbs.
Marie Da Silva, 30 and single, of Tooting in south London, is one of those who have acquired a pet during lockdown. She found her puppy Stevie - a Schnauzer-poodle mix known as a Schnoodle - at the end of December.
"Stevie is an absolute ray of sunshine. Every morning she is so excited to see me and go on her walk," says Marie, explaining that as she lives in a flat, a small dog is ideal.
"There is no way I could have adjusted to life with a puppy had there not been a pandemic. Luckily, I work in a dog-friendly office and the two months of lockdown have really helped me train her.
However, you shouldn't under estimate how demanding and time-consuming they can be. She's definitely adventurous, but nothing that some training sessions can't fix."
Jonathan Josephs, business reporter, BBC News
Dogs and cats remain the firm favourites for the 17 million homes across Britain that now have a pet. In all, 11% of households have taken on new animals. The association's survey of just over 5,000 people suggests Generation Z and Millennials are driving the increase.
This boom in animal ownership has resulted in unprecedented growth in sales for pet food manufacturers, including the two biggest, Mars and Nestlé, and has led to shortages of certain products. An industry that was already working close to capacity is now looking to expand production because, after all, a dog is for life, not just for lockdown.
The RSPCA said the boom in pet ownership could turn into a "crisis" for those animals once their owners returned to work after lockdown and could no longer lavish so much attention on them.
RSPCA pet welfare expert Samantha Gaines said: "Many of our pets are now used to having us around all the time, while others have never known any different.
"We have real concerns that life post-lockdown, both in terms of a new routine and spending time alone, could be really difficult for them to adjust to, which is why it's so important that owners start to prepare them now."
According to the PFMA, there are now 34 million pets in the UK, including:
- 12 million cats
- 12 million dogs
- 3.2 million small mammals, such as guinea pigs and hamsters
- three million birds
- 1.5 million reptiles.
In addition, another five million households keep fish in an aquarium.
For those people who are concerned about their pets' well-being once life starts returning to normal or are already struggling, the PFMA can offer advice on what to do.
It says owners in need of advice should visit its website for tips.