A tour de force; an impressive advance; years ahead of its time. When South Korean researchers declared last month that that they had created stem-cell lines genetically matched to individual patients, commentators were ready with superlatives, and rightly so. The paper (W. S. Hwang et al. Science doi:10.1126/science.1112286; 2005) is a major step towards the use of stem cells in the study and treatment of disease.

In Britain, however, many usually well-informed members of the public may be labouring under the illusion that it is their nation, and not South Korea, that is pushing back the boundaries of stem-cell research. For just as Hwang's paper appeared in press, a second one — or, at least, an abstract of one — sprang forth from a team of biologists at the University of Newcastle upon Tyne. This group, led by fertility specialist Alison Murdoch, had not matched Hwang's achievements — they merely described the creation of a cloned embryo, not the extraction of cell lines — but they stole most of his thunder in the UK press.

If this were just a routine case of domestic media favouring local achievements, it wouldn't matter much. But the manner in which the Newcastle team made its discovery public has consequences that reach beyond one day's headlines. As researchers in the field have been angrily informing Nature since the two pieces of work appeared, the approach taken in this case risks damaging science and its public perception.

The Newcastle team submitted its work to an independent Cambridge-based journal, Reproductive BioMedicine Online, which has the unusual policy of making abstracts of submitted papers available on its website as soon as the articles are sent out for peer review. The full paper is kept confidential until it is accepted and published. So science reporters informed of the findings by a telephone briefing had access to an abstract that had not been peer reviewed — and to nothing else.

It can't yet be determined for certain if the Newcastle team was intending to ride the wave of publicity for the South Korean paper, or if it simply submitted its paper to the journal at a fortuitous moment. And in an ideal world, science reporters would know the difference between a significant breakthrough and a local, incremental result.

But the premature release of this incomplete information, without any form of peer review and without making it clear to journalists that the work had not been refereed, is contrary to good scientific practice. The paper could, in principle, be revised or even rejected after peer review, in which case the public would have been misinformed. The absence of a paper also prevents other researchers from assessing or responding to the Newcastle results.

Industrial companies already release claims to the media while keeping data confidential for commercial reasons, and that's frustrating enough. The last thing the science community needs is for publicly funded academic researchers to start playing the same game. And to do so in the technically and ethically contentious arena of stem cells is playing with fire.