The Church of England sought to shed its puritanical image on sexual issues yesterday in a report that could pave the way for further liberalisation.
Its Doctrine Commission admits that the Church has "acquired a reputation for being negative about sex". It should celebrate it as "a wonderful gift from God".
Pejorative language, such as the phrase "living in sin", is absent from the report, which instead encourages "covenanted relationships".
The Rt Rev Stephen Sykes, the commission's chairman, says that any man and woman who make a lifelong commitment to each other are in such a relationship, whether or not they are married.
However, the Church will still urge such couples to marry, although it increasingly recognises that the institution is far from perfect.
The report says that the Church remains divided on whether homosexual couples can be in such relationships.
Even so, liberals will seize on the 138-page document, Being Human, which has been endorsed by the House of Bishops, to reinforce their arguments that the Church needs to relax its strictures.
The report said that, given the changes in society's attitude towards sex and relationships, "a merely nostalgic or conservative reaction is out of the question". The report also argues that people need ever greater wisdom to deal with modern pressures such as power and money.
The report concludes: "Unless the forces are understood and responded to with insight and good sense, individuals and whole families, communities, nations and regions - ultimately human life itself - are at risk."