Electoral Commission warns that local authorities continue to hit problems with management systems
The controversial switch from household to individual electoral registration may be put on hold because of "problems with the software" in town halls, the government has been told.
The Electoral Commission says it is "highly unlikely" to recommend adopting the voting rolls collected through individual electoral registration (IER) this year, as ministers hope.
The watchdog warned that electoral registration officers (EROs) at local councils are continuing to run into problems with their electoral management software systems.
The hitch does not prevent the EROs registering people to vote, but "has affected the quality of data they have been able to provide the commission".
Jenny Watson, the commission's chairwoman, said: "Our analysis has been hindered by problems with the software used by electoral administrators. Without urgent action by the government and software suppliers to address this, it is highly unlikely that we could recommend that the end of the transition to individual electoral registration should be brought forward, in our report this summer."
That report, in June, will determine whether the IER rolls will be adopted from December this year, or not until December 2016.
The warning comes in a commission analysis which found that the number of registered voters has plunged by 920,000 - or 2.2% - since the switch to IER, last summer.
And the number of 'attainers' - those approaching 18 years of age, within 12 months - has fallen by 33% from the registers in February and March last year.
In a written statement, Gary Streeter, representing the Speaker's committee on the Electoral Commission, said the decline was "likely attributable" to a lack of household canvassing last year.
Sadiq Khan, Labour's justice spokesman, said the figures confirmed Labour's "worst fears" and represented a "disaster for our democracy". He said: "They are a direct consequence of the way the Tories and Liberal Democrats hastily forced through changes to the way people register to vote."
Last year, the commission announced that "data matching" had successfully verified the details of 87% of current electors who have been transferred automatically to the new IER registers.
The details of 5.5m existing electors - or 13 per cent of the total - had not been matched or transferred, but they can vote from the old 'household' registers in May's general election.
The exception is attainers, who are too young to be on the previous rolls - so must be registered under IER, in order to vote in May.
To find missing voters, Labour has called for trials of election day registration and for local authorities to use their own data - including council tax, parking permits, council tenants and school rolls - to automatically register them.
Pictured: Polling Station in Haverhill 2007 by 159753 (Own work) [Public domain], via Wikimedia Commons