An environmental expert has found ‘dangerously high’ levels of contamination in the earth just outside the fracking test drilling site at Barton Moss, a court has heard.

Dr Aidan Foley discovered a high concentration of chemicals linked to cancer by the perimeter fence of the IGas plant in Eccles, Salford, a judge has been told.

The environmental scientist also said he found what he believes could have been drilling mud left at the back of the site.

The mud is used in the drilling process to carry rock cuttings to the surface and it must be disposed of in a controlled way because it is considered potentially hazardous.

Dr Foley’s preliminary Barton Moss report is being used by defence lawyers in a bid to get around 60 cases against anti-fracking protesters thrown out.

The expert gave evidence about his findings in a hearing at Manchester Magistrates Court today, when district judge James Prowse described how the report had found concerns over the levels of Polycyclic Aromatic Hydrocarbons (PAHs) found in earth near the test drilling site.

The judge added: “The report said you found PAHs in a dangerously high concentration in circumstances which led you to believe it probably came from the site.”

The court heard how there were fears the contamination could percolate down into the watercourse.

Dr Foley told the hearing that the contamination could have come from heavy machinery used at the IGas site but was unlikely to have been caused by the test drilling process itself.

He added it could have come from other sources – including the M62 and Barton Aerodome.

The court heard how the expert would need to get back on to Barton Moss and inside the site’s perimeter fence to take more samples to identify the source of the contamination – but that IGas and landowners Peel Holdings had so far blocked the move.

Lizars solicitors commissioned Dr Foley, of EGG Consultants, to carry out the report to help defend the anti-fracking protesters they are representing.

Richard Brigden, defending the protesters, argued that the aggravated trespass cases should be thrown out if Dr Foley is not allowed back on to the site to carry out further tests because they would not get a fair trial.

Speaking about the possibility of drilling mud being left at the site, Dr Foley said: “Drilling mud should be controlled and not spilled all over the site. Such a spillage would indicate a breach of the environmental permit.”

The court heard how an expert for the prosecution, Sarah Scott from the Environment Agency, disagreed with the findings in Dr Foley’s report – although she was not called to give evidence about it.

The case has been adjourned for District Judge Prowse to give directions as to whether the cases can proceed if Dr Foley is not given access to the site.

IGas carried out test drilling at Barton Moss last year to explore the potential reserves of shale gas beneath the earth.

The process to extract the gas - hydraulic fracturing, or fracking - sees a water, sand and chemical mix into the ground at high pressures.

It was met by a high-profile protest by campaigners who fear it could lead to contamination of water supplies.