Failure to register to vote should become an offence to stop the "real risk" of "large numbers" of people falling off the electoral roll under a planned shake-up of the system, the Government has been told.
The coalition plans to introduce individual registration following the 2015 general election, ending the current household method for submissions.
In a new report, MPs warned it would be too easy to "opt out" and voter numbers would drop. That inaccuracy in the register could "have a marked and potentially partisan effect" on boundary changes, they added.
The Political and Constitutional Reform Select Committee called for the Government to follow Northern Ireland's lead by making it an offence to fail to complete a voter registration form. It suggested the penalty could be phased out after five years once the new system had bedded down.
The committee also urged the Government to reconsider its plans not to hold a full household canvass in the year before the election, warning an "unacceptably large number of potential electors", such as those who had moved home, would be affected.
Committee chairman Graham Allen said: "Getting individuals to take responsibility for their own votes is the right thing to do, but it needs to be done in the right way. There are real risks in moving to a new system, not least that people with the right to vote could fall off the electoral roll in large numbers. The amendments which we propose - especially on the 2014 canvass and on not opting out - are essential if individual electoral registration is to command public confidence and not to be seen as unfair and politically partisan."
Katie Ghose, chief executive of the Electoral Reform Society, said: "This report is welcome reading for anyone interested in our democracy. Westminster was sleepwalking towards a catastrophic drop in voter registration. We're pleased politicians have finally woken up to the problem. These missing millions are avoidable, and the Government must now take heed."
A Cabinet Office spokeswoman said: "The move to individual electoral registration will modernise the electoral system and help to combat fraud. We welcome the committee's support for its introduction.
"We are putting safeguards in place to stop people 'dropping off' the register, as well as looking at ways we can increase registration levels.The Deputy Prime Minister has made it clear that the Government will carefully consider concerns that have been raised about the proposal to allow people to 'opt out' of being invited to register to vote for a limited period."
"We want it to be as easy as possible to register, while keeping the register more accurate and up to date. Under the new system, everyone will be invited to register in 2014 and will receive a number of reminders. If they do not respond they will then be visited at their home by an electoral registration officer to ask them to register."
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