Ministers hope to force through a change in the law within months to stop cold-call companies using unlisted numbers.

These companies will be forced to provide a valid caller ID that shows up on the recipients handset or face fines of up to £500,000. Baroness Neville-Rolfe, the minister for data protection, said that mandatory caller ID is another step as part of a closely coordinated effort with regulators, industry and consumer groups to tackle the problem.

The proposed regulation is under consultation and if approved is expected to be enforced from April.