Reams of vile online abuse aimed at Madeleine McCann's parents has been compiled in a dossier that makes for shocking reading.

Web trolls have written of their wishes for Kate and Gerry McCann to be "killed by a bus" or "trampled by horses," and that they should "burn in hell".

Even missing Madeleine's siblings have been targeted by some web users, who could face prosecution for their campaign of hate.

Messages being investigated by police include "I hope that the McCanns are living in total misery" and "I want to see them smashed up the back of a bus or trampled by horses".

Messages of violence and hatred have poured in on websites such as Facebook and Twitter, prompting fears a threat may one day be carried out.

A campaigner who helped compile the messages said: "We're very worried that it's only going to take somebody to act out of some of these discussions, some of the threats that have been made. We couldn't live with ourselves if that happened and we had done nothing," they told Sky news.

One alleged troll who was confronted on camera by Sky News insisted she was "entitled" to abuse the McCanns, whose daughter has been missing since 2007.

Scotland Yard is investigating the abuse. The police contacted campaigners, saying: "The material will now be assessed and decisions made as to what further action if any should be undertaken."

A Scotland Yard spokesman said: "We can confirm we received a letter and documentation on September 9 which was passed to officers from Operation Grange. They are assessing its contents and consulting with the Crown Prosecution Service and the McCann family."