Brooks told Cameron she 'cried twice' during his speech
Former News International chief Rebekah Brooks texted David Cameron to reveal she had "cried twice" during his 2009 party conference speech.
Two messages, passed on to the Leveson Inquiry into the media, have been published by the Mail on Sunday.
In the other, the prime minister describes a horse he has been riding.
Downing Street confirmed the text messages were authentic and said Mr Cameron had co-operated with the Leveson Inquiry into the media.
Much of Lord Justice Leveson's inquiry was taken up with questions about links between politicians and Rupert Murdoch's News International media company.
'Appeal to the heart'
After David Cameron's Conservative Party conference speech in 2009, Mrs Brooks texted him to say: "Brilliant speech. I cried twice. Will love 'working together'."
In the same year, Mr Cameron sent Mrs Brooks a text referring to her racehorse trainer husband Charlie, writing: "The horse CB put me on. Fast, unpredictable and hard to control but fun. DC."
Conservative business minister David Willetts explained Mrs Brooks's emotional reaction to Mr Cameron's conference speech, telling BBC One's Sunday Politics: "I find, when someone sets out the case for what we are doing, I do think it's not just an appeal to the head, but the heart as well."
Meanwhile, Labour MP Chris Bryant said he had written to Lord Leveson asking for all the emails and texts between Mr Cameron and Mrs Brooks to be published.
Lord Leveson has said that only those relating to the one-time proposed takeover of the broadcaster BSkyB by News International's parent company, News Corp, must be passed on to the inquiry.
But Mr Bryant told the BBC News Channel it was important to investigate the "whole of the relationship" between the press, police and politicians.
He added: "Most ordinary members of the public would think it's material whether the prime minister was texting Rebekah Brooks every day or just once every two years.
"So I think it's time we saw all the material, and then we can judge for ourselves."
However, he conceded that the prime minister was entitled to "a degree of privacy".
Downing Street said all the documents requested by the Leveson Inquiry had been handed over and that the position had not changed regarding publication.
Lord Leveson is thought to be poring over a large amount of correspondence between Mr Cameron, Mrs Brooks, and former Downing Street communications chief Andy Coulson, also a former editor of the News of the World.
But the inquiry's lead counsel Robert Jay QC has said only "relevant" documents will be published.
Mr Cameron and Mrs Brooks live near each other in Oxfordshire and Mr Brooks went to Eton with the prime minister.
Mrs Brooks caused amusement at the Leveson Inquiry earlier this year when she revealed that Mr Cameron signed some of his texts LOL, thinking it meant Lots Of Love, rather than Laugh Out Loud.
The two messages published by the Mail on Sunday were sent in October 2009, shortly after Mrs Brooks became chief executive of News International. They were among a number of texts and emails handed over to the Leveson Inquiry by Downing Street and Mrs Brooks.
In her evidence to Lord Justice Leveson, Mrs Brooks said Mr Cameron had sent her a text when she resigned in July 2011, telling her to "keep your head up".
She quit after the phone-hacking scandal led to the News of the World's closure, a paper she was editing when voicemails of murdered schoolgirl Milly Dowler's mobile phone were intercepted.
It also emerged that Mr Cameron rode a police horse, Raisa, which had been lent to Mrs Brooks by the Metropolitan Police.
Mrs Brooks and Mr Coulson are awaiting trial accused of conspiracy to access voicemails. Mrs Brooks and her husband are also charged with conspiracy to pervert the course of justice.
The Leveson Inquiry is due to publish a report later this month.