Mr Miliband was campaigning in Oldham East and Saddleworth for a third time ahead of Thursday’s by-election.
He told party volunteers voters could “send a message” about tuition fees, police cuts and the VAT rise.
David Cameron has rejected claims the poll amounts to a referendum on the Lib Dem-Conservative coalition.
The by-election was called after former Labour minister Phil Woolas’s victory in May was annulled by a court.
Speaking to Labour supporters on Saturday, Mr Miliband said: “For the first time since this Conservative-led government was formed, voters will have their chance to pass judgement on David Cameron and Nick Clegg.
“They can send a message about the betrayal on tuition fees. They can show the government what they feel about police cuts both here and across the country.
It is important people who want to send a message to the government turn out in this by-election”
End Quote Ed Miliband
“And they can make clear their anger about a VAT rise which is the wrong tax at the wrong time.”
He later knocked on doors, chatted and shook hands with households, accompanied by Labour candidate Debbie Abrahams.
Lib Dem leader Mr Clegg has visited Oldham twice and the prime minister visited on Thursday.
The poll is being closely watched by analysts who see it as the first major test of how the two coalition parties intend to campaign against each other.
During Mr Cameron’s visit, he denied the Tories were soft-pedalling in the seat to give the Lib Dems a better chance and said his party would fight very hard for every vote.
He denied it was a “token” gesture, claiming he was the first prime minister in the last 10 years who had been to a by-election in England.
Lib Dem candidate Elwyn Watkins lost the seat in the May General Election by 103 votes.
But Mr Woolas’s victory was annulled when an election court ruled he had made untrue statements about Mr Watkins in campaign leaflets.
Mr Woolas was then dropped by the Labour Party after losing a legal challenge.
Although Mr Watkins is Labour’s nearest challenger, the constituency was a three-way marginal in May with Conservative Kashif Ali – who is standing again – fewer than 2,500 votes behind.
Since then, the Lib Dems’ fortunes have plummeted in national polls after the furore over tuition fees.
Mr Miliband said: “It is important people who want to send a message to the government turn out in this by-election.
“The stakes are too high to stay at home. The danger is if they stay at home they end up with a Lib Dem or Conservative MP by the back door.”