Proposed new election security measures do not go far enough and could lead to fraud, the Conservatives have said.
Postal vote registration has proved controversial
The Electoral Commission has demanded individual voter registration after last year's local elections were marred by voting fraud.
But the government does not favour that plan, fearing it would lead to a fall in the number of registered voters.
In a series of trials, people will have only to sign their own registration form and give their date of birth.
Shadow constitutional affairs secretary Oliver Heald said ministers had not done enough "to safeguard democracy" under the plans.
"Fiddling with the electoral system" had compromised democracy in Britain, Mr Heald said.
"[Ministers] have refused to introduce the tried and tested system of individual registration, as used to cut fraud in Northern Ireland," he added.
Voters will not have to provide National Insurance numbers to secure a ballot paper, as they do in the Northern Ireland system.
Ministers believe such a scheme could cut already low electoral roll numbers.
Lord Chancellor Lord Falconer said the Northern Ireland system could not be copied straight over because of "different practices and traditions in relation to registration".
"Our concern is that we don't want to do anything that undermines a register that is already clearly incomplete and we have other measures to do with security," Elections Minister Harriet Harman said.
She insisted there had been a cross-party, non-partisan approach to looking at the Electoral Commission's recommendations and the problem.
The commission says the current "outdated" system of household registration is open to abuse.
Chief executive Peter Wardle said he was disappointed that the "fundamental recommendation" of individual registration had been left out.
"It wouldn't be considered acceptable for someone else to vote for you, so it shouldn't be acceptable for someone else to register on your behalf," he said.
Voters could not have full confidence in the security of the postal voting system without such action, he added.
Liberal Democrat spokesman David Heath said the Bill was "a disappointment to those who were hoping for a more rigorous overhaul of the system".
Post vote abuse
Last year, six Birmingham councillors were forced to step down after the commission found evidence of postal ballot abuse.
One councillor was later cleared, on appeal, of corrupt practices.
Commissioner Richard Mawrey QC upheld allegations of postal fraud relating to the ballot of 10 June last year.
Measures proposed as part of the new Electoral Administration Bill include a register of postal ballots received, warnings about people keeping their vote secret and improved security markings.
Officials will have new duties to have a complete register and will be given the power to encourage people to vote.
The new Bill will also cut the age limit for candidates from 21 to 18 and allow parents to take their children into polling booths to show them how to vote.