PRINCE Charles's attorney general fought off a High Court bid to take the Duchy of Cornwall to court over oyster farming activities in a conservation area.

Businessman Michael Bruton, from Port Navas, Falmouth, was ordered to pay the Prince's legal team £7,500 in costs after a judge ruled that he had delayed too long in launching his legal challenge.

But Mr Justice Burton, sitting in London, said Mr Bruton could seek judicial review against Natural England, which was responsible for regulating a site of special scientific interest (SSSI) within the conservation area.

Mr Bruton, who described himself as "an environmental activist", challenged the legality of the Duchy granting a licence to Duchy of Cornwall Oyster Farm Ltd to cultivate non-native Pacific oysters in the Lower Fal and Helford. His lawyers argued non-native oyster cultivation posed a serious threat to the local habitat and the Duchy should have ensured an "appropriate assessment" was carried out under the EU Habitats Directive.

The Prince's attorney general, Jonathan Crow QC, replied that, in the circumstances of the current case, the Duchy "does not have any function in relation to the environment at all". Mr Crow also submitted that the oyster farm project was known about by the public as far back as 2005, but it was not until 2008 that he made his complaint.

Refusing Mr Bruton permission to seek judicial review against the Duchy, the judge agreed, saying: "I am satisfied there has been unexplained delay in this case".

The court was told oyster fishing in the tidal waters of the Helford River dated back many centuries. The river bed and oysterage rights had always been privately owned and were early last century conveyed to the Duchy, which had since leased the rights to tenants.

The Duchy has been an estate for the eldest sons of the monarch since the days of William the Conqueror.

Paul Lasok QC, for Mr Bruton, told the court there was a clear risk that, even though the Pacific oysters being farmed were said to be infertile, it was accepted there was a risk they might spawn.

Mr Lasok said: "They are particularly invasive. They get everywhere. There is a risk that they would get into parts of the SSSI and destroy habitats and other features the SSSI is there to protect."

Mr Bruton's lawyers applied for a "protected costs" order to ensure he would not be liable for Natural England's legal bill if he pursued his case against the organisation and eventually lost it.

Natural England estimated that if the case against it went ahead, its final legal bill would be about £40,000. The judge made a limited protected costs order, covering Mr Bruton for no more than £15,000 of Natural England's costs.

He recognised that Mr Bruton was putting forward an environmental point that he felt strongly about, but said he did not think he should be able to do so without any financial risk.

After yesterday's hearing, Mr Bruton said that, before finally deciding whether to pursue his claim against Natural England, he would have to consult his legal team and find out whether other people in the Lower Fal and Helford area were prepared to back him financially.