A Labour MP has been fined up to £5,000 after making 35,000 nuisance calls during an abortive bid to be the party's London mayoral candidate.
The calls, which played a recorded message urging people to back David Lammy's campaign, were placed over just two days last August.
Information Commissioner Christopher Graham found Mr Lammy broke privacy rules because he did not have permission to contact the individuals.
Mr Graham said: "The rules apply to political groups canvassing for votes in the same way they apply to salespeople offering a discount on double glazing. If you want to call someone in this way, you must follow these rules. Mr Lammy did not, and that is why he has been fined.
"It's not good enough to assume the people you're contacting probably won't mind. The law requires you to have permission before making calls with recorded messages. And if the law isn't followed, the regulator will act."
If Mr Lammy pays by April 5 the fine will be reduced to £4,000.