Before the address almost four times as many people were criticising Cameron than praising him. Social media monitoring firm Talkwalker reported that sentiment was 49 per cent negative and 13 per cent positive.
Opinion moved sharply in the Prime Minister's favour after the speech to 34 per cent negative and 27 per cent positive.
The reputational benefits of the speech, in which he promised to raise the 40 per cent tax threshold to £50,000, were largely limited to Cameron, while attitudes to the Conservative Party changed to a much lesser degree.
Before the speech 48 per cent of social media comments about the party were negative and only 11 per cent were positive. Afterwards they were still 46 per cent negative though positive comments rose to 17 per cent.
Robert Glaesener, CEO of Talkwalker, said: "The response to the speech was quite remarkable. He has clearly done a very good job of persuading social media that he is credible on tax cuts, Europe and the NHS. Social media is a good indication of something brewing up from the bottom.
"Our analytics on more than 75,000 mentions show that as the general election approaches, social media is already picking up the main topics – such as UKIP, NHS,and taxes – that will be debated in the coming months."