Theresa May described Labour as a "laughing stock" as she and Jeremy Corbyn met at Prime Minister's Questions for the first time since the summer recess.
Mrs May poked fun at the Labour leader on several occasions, including over the "traingate" saga.
Mr Corbyn, who faces a leadership challenge from Owen Smith, used his questions to ask the prime minister about the "housing crisis" in Britain.
Last month, Mr Corbyn was filmed sitting on the floor of a train complaining about "completely ram-packed carriages".
But CCTV was later released showing him appearing to walk past empty seats.
Mrs May used the incident to mock Mr Corbyn and his party at PMQs, saying: "The train has left the station, the seats are all empty, the leader is on the floor - even on rolling stock they're a laughing stock."
She also drew laughter from her Conservative MPs when she highlighted the response Mr Corbyn got when asking his Twitter followers for questions to ask in the Commons.
"I thought I would look to see what sort of responses he'd received," she said.
"Lewis writes 'Does she know that in a recent poll on who would make a better Prime Minister, don't know scored higher than Jeremy Corbyn?'"
Mr Corbyn spent the session questioning Mrs May about housing.
He warned that the average house price in Britain is £215,000 - more than eight times the average wage - and said the "dream" of home ownership had become "just that" for many people.
Mrs May said house building was up under the Conservative government - something Mr Corbyn disputed - and added that the Government was helping people buy their first home.
The Labour leader also said only one in every five council houses sold under Right to Buy is replaced, short of the Government's "one-for-one" pledge.
Mrs May claimed this was wrong and that the commitment has been delivered.