As Electoral Registration Officer, you have a duty to maintain an accurate and complete register. UK law enables you to require anyone to provide information required for the purposes of your registration duties.
In particular, Regulation 23 of the Representation of the People Regulations 20011
states that: A registration officer may require any person to give information required for the purposes of that officer's duties in maintaining registers of electors.
Under data protection principles the ERO is entitled to collect the required information as there is a lawful basis for its processing; the performance of a public task in the public interest, as provided for in electoral law.
If any additional optional information, for example email addresses and phone numbers, is requested, this may be shared if a data sharing agreement is in place between you and the responsible person or organisation, and they have informed individuals about the potential sharing of such information through their privacy notice.