Research involving human embryonic stem (ES) cells is once more under scrutiny in Europe. In a situation that will stir memories of the acrimonious debates of 2006, legislators must again assess whether this kind of work should still be funded under the forthcoming €80-billion (US$100-billion) Horizon 2020 research programme.

Now, as then, opinion is split. Some countries and some members of the European Parliament are in favour of the research, recognizing the long-term potential to treat debilitating disease. Others maintain that it is immoral to exploit a technique that uses human embryos — even spare embryos from in vitro fertilization clinics that would otherwise be destroyed, and from which nearly all experimental human ES cell lines are derived. The 2006 debate was resolved with both the European Parliament and Council agreeing to fund such research, provided that it didn't involve the creation of new human ES cells, and provided that it was not carried out in those countries — such as Germany — whose national law banned it.

Stem-cell researchers around the world breathed a sigh of relief, knowing how a decision in Europe could also influence funding decisions elsewhere. The outcome of the present debate offers similar influence. But there are already signs that some members of the European Parliament will once again try to outlaw funding of research involving human ES cells.

Rather than wait for these views to gain unchecked momentum, a group including UK research-funding bodies the Wellcome Trust, the Medical Research Council, the British Heart Foundation and Parkinson's UK last week issued a joint statement in support of the research, explaining the benefits of the work and the rationale to include it in Horizon 2020.

The general public, and politicians, have every right to question whether the ends justify the means used by medical researchers.

It is a wise move that should help to anchor the coming debate to reality. Biology is complicated, which makes it easy for politicians to mislead the public and colleagues — intentionally or unintentionally — in emotive areas. The general public, and politicians, have every right to question whether the ends justify the means used by medical researchers. But they also have the right to reliable information.

The statement outlines the remarkable progress that stem-cell researchers have made since 2006, which has led in the past 12 months to the first approvals for clinical trials of potential therapies involving human ES cells — for a type of blindness called macular degeneration and for spinal-cord injury. In addition, scientists have discovered how to force adult cells back to an embryonic-like state. The resulting induced pluripotent stem (iPS) cells can then be grown into particular cell types and used to understand mechanisms of disease at the cellular level. In the long term, they may also be useful for therapy.

The most insidious claim of those who oppose human ES cell research holds that iPS cells, which can be derived from a particular patient's own cells and are ethically unburdened, eliminate the need for human ES cells in research and therapy. That concept sounds appealing, but it is simply not true. Scientists understand little of the differences between the two sorts of stem cells and it will take years of comparative work to do so.

One particular event that makes biomedical researchers worry is a decision taken last year by the European Court of Justice. In October it ruled that patenting of inventions involving human ES cells was illegal because it was immoral — and as a consequence, human ES cell research must also be immoral (see Nature 480, 310–312; 2011). Nature condemned this ruling as being beyond the court's juridical and technical competencies (see Nature 480, 291–292; 2011). But members of the European Parliament who oppose human ES cell research stealthily inserted a reference to it during an unrelated resolution on broad patenting of essential biological processes in animal and plant breeding, which was adopted on 10 May.

Horizon 2020 has to be approved by the European Parliament and Council by mid-2013 so that first calls for proposals can be launched at the start of 2014. The UK research funding agencies' statement is a good start to a continuous campaign of education and transparency that stem-cell researchers from all interested European countries must maintain for the next year. Just as cell-culture medium needs to be renewed to keep its cargo alive, a political message has to be constantly renewed if it is to stay alive in political minds.