Family courts across England and Wales are being opened up to journalists as part of a government bid to boost public confidence in the system.
Justice Secretary Jack Straw said the move was a step towards a new culture of "greater openness" in all courts.
But news organisations have complained that many cases will remain unreported, because judges still have wide powers to restrict reporting and media access.
Ministers say they will legislate to relax reporting restrictions in time.
Family courts make far-reaching decisions, such as whether children should be taken into care or put up for adoption, or given contact with parents who are divorcing.
They also decide on custody and how finances should be split.
Until now, with some exceptions, neither the public nor the media have been allowed in, to protect families - particularly children - from intrusion into their privacy.
But there have been claims that the secrecy of the hearings has led to injustices, with some children taken wrongly into care.
From Monday morning, accredited journalists in England and Wales will now be allowed into many more family hearings, to witness what is being said and done.
Judges will also have the power to relax reporting restrictions in individual cases or limit what can be reported to protect the welfare of children and families.
Youth court rules
Mr Straw said: "Family courts play a crucial role in our society. It is vital that these courts command the confidence of the public. If justice in these courts is seen to be done, they will be trusted by the public.
"Existing reporting restrictions for the newly attending media will of course still apply to protect children and families, but I want to ensure a change in the culture and practice of all courts towards greater openness, and this is an important step towards that goal."
Last December, Mr Straw told MPs that journalists attending family courts would be governed by reporting restrictions similar to those applying to youth courts.
Under youth court rules, it is unlawful to publish anything that would identify a juvenile involved in a case, but it is possible to identify adults such as social workers and doctors.
However, changes to allow the identification of such adults have not yet been made and journalists argue the opening up of the courts has therefore been pointless.
'No real change'
The Newspaper Society and the Society of Editors, supported by the BBC, ITN and the Press Association, have written to Mr Straw, saying the effect "will be to nullify... the government's stated aim of openness and accountability".
The letter continued: "The great majority of the very cases in which public concern is most acute are those which involve children, and particularly state intervention in children's care and upbringing."
Under current rules "these proceedings would not be reportable and effectively there would be no change at all", it added.
The Ministry of Justice said it would be legislating to revise reporting restrictions "as soon as Parliamentary time allows".
Until legislation revising reporting restrictions is in place, reporters will be able to report sufficient outlines of cases to allow readers to understand "the gist of proceedings without identifying those involved", a spokesman said.