Around 800,000 people have dropped off the electoral register since the new system of individual sign-ups was introduced, while students have been the worst hit, according to Labour.
The party said students in particular were a "casualty" of the move away from household registration after an analysis suggested some university cities had seen electoral roll reductions of up to 13%.
The Government previously defended the decision to finalise the individual electoral registration (IER) change in time for polls in May this year, saying it would remove "phantom voters" and reduce electoral fraud.
But Labour's shadow minister for young people and voter registration Gloria De Piero said: "About 800,000 people are missing from the electoral register. The government ignored independent warnings not to rush through IER, and now it appears that students are a casualty of their hasty changes.
"The Government can act by issuing guidance to universities to support them with voter registration – we hope they listen."
De Piero and the National Union of Students had warned the government about the potential effects of the change in November, saying it threatened to "disenfranchise and shut people out of our democracy".
In the past, it was possible for a family member or university to register on a student's behalf, however now individuals have to take action themselves.
De Piero has written to constitutional reform minister John Penrose calling for universities to be issued guidance to offer voter registration to students when they enrol.
She said areas including York, Cambridge and Dundee West were among the worst affected by the switch to IER and also cited Sheffield University's opt-in initiative as a model for other institutions.
Some 67% of Sheffield students were registered, the MP said, and uptake at universities in Cardiff and Leicester also had a "big impact".
In the letter, she said: "As you will know, IER prevents universities from block registering all their students in halls of residence, but measures should be taken to ensure that it is as easy as possible for individual students to register.
"I write to you today to call for official guidance to be issued to every vice chancellor in the country about how they can adopt the Sheffield model in their universities for next year's enrolment.
"This would be an important step forward in rectifying the big drop in student registration and representation resulting from the Government's rushed changes to voter registration."
Before the move to IER was completed earlier than planned last year, the Electoral Commission warned that the truncated transition process could leave some of the 1.9 million people still listed under the previous regime without a voice.
But Penrose said allowing "carry forward" electors to remain eligible for longer "will pose an unacceptable risk to the accuracy of the register".
Martin Doel, CEO of the Association of Colleges said: "Young people have a significant electoral influence and with the government making crucial decisions that will affect their future it’s important they have a voice. We will be working with colleges to encourage students to register to vote to ensure their voice is heard."