General election 2015: Hidden cameras used in new voter registration advert
The Electoral Commission says it has turned to "behavioural economics" to try to persuade people to register to vote at the general election.
An advert shows people being stopped from doing things they thought they were able to do, like walking through a park and pouring ketchup on their food.
The advert, partly filmed with hidden cameras, is to highlight the 20 April deadline to register to vote.
Nearly 70% of people are unaware of the deadline, the commission said.
It recently said the number of entries on the electoral register had dropped by 920,000 between March and December last year.
For its latest campaign, the watchdog said it was using the concept of "loss aversion", saying: "In certain situations people are more likely to be motivated by realising they may lose something, than the prospect of making a gain."
It has also published a survey showing that 40% of people thought it was not possible to register to vote online in England, Scotland and Wales. In fact, the government has said record numbers have used the service.
It also found that 13% of people thought it was already too late to register.
Jenny Watson, chairwoman of the Electoral Commission, said: "A general election can prompt a great deal of excitement and debate, with voters keen to have their say.
"But there are a lot of misconceptions, with many people not realising they aren't registered or how easy it is to do."
How to register to vote
You can register once you are 16 although you will only be able to vote on 7 May if you are 18 or over on the day.
If you are a citizen of another EU member state or Commonwealth country living in the UK, and unsure whether you are entitled to vote in the general election or local elections check the Electoral Commission website.
You can register to vote online through the government's gov.uk portal. The process takes five minutes and you will need your National Insurance number.
If you are unsure whether you are already registered or want to update your details, contact your local electoral registration officer to find out. You can also register to vote by post.