Housing Secretary Michael Gove said the Labour leader’s changing stance on Brexit showed he was “transparent, spineless, and swept along by the tide” like the marine animal.
He added a Conservative government has “never been more necessary than now” and is able to deliver the long-term changes the country needs.
Mr Gove said that although the Government was on track to build one million new homes in the current parliament, “many more” homes needed to be built.
He told delegates that the Conservative Party had a “record to be proud of”.
The Cabinet minister said: “It is a record that everyone of us should be proclaiming every single day from now until the next general election because this is a record which will give us victory.”
“We will take the fight to the Labour Party. The party of Jeremy Corbyn and his self-proclaimed friend Sir Keir Starmer.
“Sir Keir, who was against Brexit, then wanted to accept Brexit, then wanted a second referendum on Brexit, then he said that he wanted to make Brexit work, and then just last month, he said he wanted a Brexit which was actually identical to EU membership.
“He was saying, as he always does, whatever he thought people in the audience wanted to hear.
“Sir Keir Starmer is the jellyfish of British politics. He is transparent, spineless and swept along by the tide.”
Mr Gove told Labour that the Tories will “fight, fight and fight again” for the UK’s future.
Work and Pensions Secretary Mel Stride branded Sir Keir a “Marxist” while speaking at the Conservative Party Conference.
He said: “The reality is, you and I know exactly why Captain Hindsight can’t make up his mind when it comes to welfare.
“It’s because his own instincts are totally out of touch with the majority of the British people.
“Rather like Jeremy Corbyn, Keir Starmer truly is a Marxist. Because as Groucho Marx put it, ‘I have principles, but if you don’t like them…well, I have others’.”
Prime Minister Rishi Sunak also claimed the opposition leader’s approach was to “flip-flop on everything” and “don’t stand for anything”.
He added: “I don’t think that’s leadership”.
Home Secretary Ms Braverman also hit out at Sir Keir.
Looking ahead to the next general election, she said: “The British people will get to decide if they want to curb woke with Rishi Sunak or let it run riot with Keir take-the-knee Starmer.”
Labour will hit back when their party conference begins on Sunday in Liverpool.