Speaking to ITV News Political Correspondent Libby Wiener, Sir Ed Davey said: "Boris Johnson betrayed the care sector and those care workers and the people in those care homes."
His comments come a day after being elected as the leader of the Liberal Democrats party, the fourth leader the party has had in five years.
The former Cabinet minister said: "My dad died when I was four, my mother became terminally ill when I was 12 and I was a young carer for her until I was 15 and I had to look after my grandmother and I've got a disabled son now, who my wife and I care for."
"I do understand about caring and one thing I think society has seen during the Covid crisis is we need to understand the care sector more, we need to invest in social care, we need to treasure the workers in our care sector," the Kingston and Surbiton MP added.
Sir Davey said: "When Boris Johnson said protect the NHS, no one objected and the NHS have been fantastic.
"But Boris Johnson betrayed the care sector and those care workers, and those people in those care homes and we've seen a tragedy in Britain's care homes.
"I want as Liberal Democrats for us to be championing care homes and telling the government to do more and to champion caring and to champion looking after bereaved families."
The 54-year-old added: "One thing I've campaigned on throughout my life is bereaved families, not in a very public way, you may not have noticed."
"But behind the scenes I've been working with bereaved charities, particularly children who have been bereaved."
He continued: "This is something that I feel passionate about, I know a little bit about and I want to use my experience to work with the 10 million carers in Britain to be their voice, to be their champion."