Sir Elton John thinks social media companies have a huge role to play in the fight against HIV and AIDS.

The 71-year-old star - who has been heavily involved in the fight against AIDS for decades - has made the plea to technology firms during his Diana, Princess of Wales Lecture on HIV at the Institut Francais in London.

He explained: ''I am used to putting pressure on pharmaceutical companies. I am used to putting pressure on governments. We have had some success with both.

''The pressure now needs to be applied to the tech giants - not because I think they are bad, but because they have the capacity to do so much good.''

Elton explained how his good friend, the late Princess Diana, was able to change perceptions of AIDS through her own activism.

He shared: ''She did not distinguish between 'us' and 'them.'''

And Elton insisted that tech firms like Facebook - which boasts a huge global reach - have a major role to play in influencing thinking and helping to raise awareness of health issues.

The 'Rocket Man' hitmaker said: ''At a stroke we can reach two billion people in a single moment on Facebook ... imagine all that power to connect turned into billions of handshakes, all over the world.''

Elton called on the owners of big social media companies to throw their support behind the fight against HIV and AIDS.

He said: ''The geniuses who created this industry must not hide behind its anonymity.

''They must use their power to help shape a new digital world ... How incredible if they could start with something as pernicious, as lethal, as the stigma of AIDS.''