Sir Ed said the Conservatives had used people as "playthings" during a tumultuous summer that saw three prime ministers in two months.
"The faces at the top may change, but all the same problems remain," he said.
Calling for a general election, Sir Ed said his party would "end the chaos".
In a speech to Lib Dem party members, Sir Ed said the Conservatives "almost bankrupted Britain" with "unfunded tax cuts for the super wealthy".
Former chancellor Kwasi Kwarteng was forced to scrap much of his mini-budget after it spooked financial markets.
In the days after the statement on 23 September, the pound fell to historic lows against the dollar and the cost of government borrowing increased.
"Instead of tackling the cost of living crisis seriously, they chose to treat the British economy as their own personal playground," Sir Ed said.
"Using people as playthings in their reckless game of fantasy economics."
The Lib Dems cancelled the party's autumn conference following the death of Queen Elizabeth II.
The conference had been due to begin during the period of national mourning and clashed with the state funeral on 19 September.
Over the past week the party has announced a series of new polices, including offering struggling homeowners a £300-a-month grant to pay off mortgages.
In his speech, Sir Ed also called for the government to abolish Ofwat, the water services regulator, over its failure to prevent sewage being dumped into the UK's waterways.
The Lib Dems' plan "is about innovation, investment, trade and people", he added.
He said: "Liberal Democrats are leading the charge for new defences for Britain.
"We must fortify our nation - not just with troops and submarines, but with wind turbines, solar panels and tidal power.
"And we must insulate every home - not just from the cold, but from the cost of [Russian President Vladimir] Putin's gas war."
Sir Ed said his party "will be ready" when the next election is called.
Unless an earlier one is called, the next election isn't due until January 2025. Opposition politicians have been leading calls for a general election, following Liz Truss's resignation.
In a direct attack on the prime minister, Sir Ed said: "Rishi Sunak, your government does not have a shred of credibility left.
"If you had a shred of integrity left, you would call a general election now.
"Being scared of the Liberal Democrats isn't a good enough reason to deny the British people their say."
In the last year, the Lib Dems have won a series of by-elections, taking seats in the House of Commons off the Conservatives - including overturning a 24,000 vote majority in Tiverton and Honiton in June.
Mr Sunak "knows we will do it again - in seats along the Blue Wall, and right across the country", Sir Ed said.
He also committed the party to ending the current first past the post (FPTP) voting system.
He said the Lib Dems must introduce a form of proportional representation - where seats in parliament are allocated so that they are in proportion to the number of votes cast.
In 2011 the Lib Dems, campaigned to replace FPTP with an Alternative Vote system but were defeated.
Sir Ed Davey: If PM has any integrity he'd call an election