Wales and Westminster have clashed over the commercial growing of genetically modified maize with Environment Minister Carwyn Jones refusing to follow London's line.
Wales is legally unable to declare the country GM-free
His statement came just hours after UK Environment Secretary Margaret Beckett told Parliament on Tuesday that ministers had agreed in principle to the growing of the GM maize after years of bitter national debate.
But underlining his commitment to the most restrictive approach legally possible, Mr Jones told Assembly Members he could not agree to commercial cultivation of Chardon LL because he wanted stronger rules on so-called "coexistence" - to ensure conventional or organic crops were not contaminated.
He also said each GM application would need to be agreed individually and after a "comprehensive assessment by all EU member states".
His stance was, he added, "clear, unambiguous" and that Cardiff Bay's position on the commercialisation of GM crops remained unchanged.
Without Wales' agreement Chardon LL cannot be put on the UK seed list (the national list of varieties).
But, Mr Jones added: "This does not mean that we can declare Wales GM free - as many would like. To do so would be illegal and it would be irresponsible for any government to work outside the legislative framework."
Carwyn Jones making his statement
The Scottish Executive is supporting the Westminster government - the executive has said that GM maize can be grown in Scotland but only after Westminster seeks an amendment to the regulations on growing the crop.
Mrs Beckett said her approach was "precautionary" and "evidence-based" and there was "no scientific case for a blanket approval for all uses of GM... and no scientific case for a blanket ban on the use of GM".
Chardon LL is a type of fodder maize and it appeared to outperform conventional maize in the evaluations by allowing more wildlife to survive, although the result is contested.
Mrs Beckett was asked by Plaid Cymru MP Simon Thomas in the Commons if Scotland and Wales would be allowed to maintain GM-free status.
She said that farmers could set up GM-free zones but this would not extend to the "arbitrary designation of a whole geographical area".
It is understood that the assembly environment minister was angered by Mrs Beckett's GM maize announcement, and that he believes it goes contrary to an agreement between his officials and those at the Department for Environment, Food and Rural Affairs.
Mr Jones has been discussing the possibility of regulations such as separation distances between a GM crop grown near conventional and organic crops.
While Mrs Beckett said the GM maize could be sown as early as Spring 2005, Mr Jones later said that it would be "not that soon" in Wales and going through the normal assembly procedures would take some months.
Mick Bates, the Welsh Liberal Democrat countryside spokesman, described it as a "Trojan Horse crop. Once this is allowed in, it will mark the end of any dream for a GM-free area."
Glyn Davies, Conservative environment spokesman said there was a terrific pressure on the minister and he seemed to be implying that the door may
be open for GM maize, if the scientific bodies backed it.
"What everybody wants is for Chardon LL not to be listed and it won't be if he stands his ground," said Mr Davies. "If he agrees for it to be listed he will be roundly criticised."
Former UK government GM crop adviser Professor Denis Murphy, head of biotechnology at the University of Glamorgan, said he was not quite sure where the assembly government got its scientific advice from.
He said he was surprised to hear Mr Jones mention the issue of health and the environment, when the evidence suggested GM maize had a positive effect on the environment.
But Brian Walters, vice president of the Farmers Union of Wales and an organic dairy farmer in Carmarthen, said he was very alarmed that a herbicide-resistant variety was being considered, with no limit on the number of times a farmer could spray the crop.