More than 100,000 extra people every year would sign up to become organ donors if they were asked to do so in the right way, a pioneering government trial has found.

For years the NHS has grappled with the conundrum of how to increase the number of people on Britain’s Organ Donor Register. Surveys show that 90 per cent of us support the principle of donation – but yet only a third bother to join the register. On average three people a day die because there are not enough donors.

Now a government team has discovered that by making small changes to the language used to ask people to become donors they can make a vast difference to the number of people signing up. Perhaps unsurprisingly, appeals to self-interest win the day.

In one of the largest ever trials conducted, more than one million people renewing their tax disc or registering for a driving licence online were randomly presented with one of eight different messages encouraging them to join the Organ Donor Register.

The study, which was conducted by the Government’s Behavioural Insights team or “Nudge” Unit, found that people were most receptive to messages that appeared to affect them personally – rather than “peer pressure” or “shock value”.

As a result of the trial – and the changes to the website which have now been implemented – it is estimated that more than 100,000 extra people a year will carry donor cards. The randomised trial worked by testing a series of messages and pictures on a website page to which people were directed after renewing their vehicle tax or registering for a driving licence. The trial ran for five weeks, during which time more than one million people saw one of the variants, making it one of the largest trials ever conducted in the UK public sector.

It found that the least successful message was: “Every day thousands of people who see this page decide to register [as an organ donor],” which ran alongside a picture of a group of smiling people. Not much better performing was the slogan: “You could save or transform up to nine lives as an organ donor.”

Even “Three people die every day because there are not enough organ donors”, was not the best way of getting people to sign up.

The most successful slogan was one which read: “If you needed an organ transplant, would you have one? If so, please help others.”

On average people who saw that message were almost a third more likely to sign up than those who saw the lowest-ranking version. The “winning” text has now become standard on the DVLA website.

The study is the latest to be published by Behavioural Insights team which has already had considerable success across other areas of government policy.

Since its creation in 2010 it is credited with saving the UK Courts Service £30m a year – increasing the number of people who paid their fines by sending them personalised text messages.

It has also worked with jobcentres to devise new programmes to help people find work. In trials, 20 per cent more people found work having been on the “Nudge” programme compared with traditional methods.

The unit is currently being “spun off” from the Cabinet Office into a new mutual company so that it can expand its work – both in the public and private sector – and provide revenue to central Government.

Francis Maude, the Cabinet Office minister, said the spin-off would contribute to growth by combining the benefits of private sector experience and investment with “commitment and innovation”.

“This study shows yet again they can make a real difference. Organ donation can transform people’s lives so I’m pleased the team has examined how we can improve sign-up rates,” he said.

Professor Anthony Warrens, president of the British Transplantation Society, said they were excited by the findings. “We have a responsibility to help people understand what an amazing act it is to donate organs and how it can transform the lives of so many others, and we very warmly welcome publication of this study on how to improve the way we ask people to join the Organ Donor Register.”

Art of persuasion: the tested phrases

Most successful phrases:

The most effective variant used the concept of reciprocity and asked: “If you needed an organ transplant, would you have one? If so, please help others.”

The second most successful used the idea of loss and was framed: “Three people die every day because there are not enough organ donors.”

Least successful phrases

The phrase: “Every day thousands of people who see this page decide to register” performed better on its own than when it was paired with a group of people. This is the opposite of what researchers expected, which may be because people thought the use of a stock photo implied it was a marketing gimmick.

The other least effective phrases were: “If you support organ donation please turn your support into action”; and: “You could save or transform up to nine lives as an organ donor”.