The report found anti-voting measures had an adverse impact

The study published on Tuesday was carried out by the Electoral Commission earlier this year, but its release was delayed until after the assembly election.

The need to register every year was brought in by the Electoral Fraud Act 2002.

In the past, one form was given to every household, but now everyone has to register individually.

The commission said this measure tended to have an adverse impact on disadvantaged, marginalised and hard to reach groups.

'DISADVANTAGED' GROUPS Young people Students Those with learning disabilities Residents in poorer areas Policing the electoral register

It meant young people, students, people with learning disabilities and those living in poorer areas were less likely to register, according to the government-appointed watchdog.

The chief electoral officer believes reinstating part of the old system - whereby some names were "carried forward" by one year - could help prevent 150,000 voters dropping off the register.

However, the commission said it was not convinced this would work.

Voting register

The report also called for a review of the special hearings procedure for those who want to be added to the electoral register.

It said the practice was unique to Northern Ireland.

The new system that is in place - and the register published for the last election - is a very sound, a very robust register Seamus Magee Electoral Commission

Thousands of people who applied to get their names added to the voting register were asked to attend such hearings.

The commission says less than half of them showed up, suggesting that they were put off by the hearings' "semi-judicial nature".

The head of the Electoral Commission, Seamus Magee, said more than 70% of people surveyed felt the new measures had instilled greater confidence in the democratic process.

"On the other hand, there are some negatives. One of those is that the individual registration has tended to make it more difficult for young people in particular and for people with disabilities to register," he said.

"The challenge that we have is to address those particular issues - to ensure the registration rate, which is currently around 88%, is up as close into the 90s as we can."

Mr Magee said it was important to get the message across that people needed to continue to register on an annual basis.

"The new system that is in place - and the register published for the last election - is a very sound, a very robust register.

Paul Murphy welcomed the commission's report

"Albeit, it doesn't contain all those who are eligible to vote in Northern Ireland. To actually carry forward - as was the old system - and inflate the register is not possibly the best way to go.

"We would have a different view than the Chief Electoral Officer on this matter."

Secretary of State Paul Murphy described the report as "an impressive study".

"I note that the commission does not agree with the assertion that 120,000 people were disenfranchised as a result of the new legislation.

"I am also pleased that the report concludes that the 2002 register more accurately reflects those entitled to be registered"'

He added: "I welcome the fact that public confidence has increased as a result of the Act. But we cannot become complacent and there is still work to be done to ensure that all those entitled to vote, take the opportunity to register."

Sinn Fein MP Martin McGuinness said it was "very obvious to anyone involved in the recent election campaign that the current system is deeply flawed".

"It is my intention to meet with the Electoral Commission in the time ahead to discuss the many problems which we encountered during the recent campaign."