At the hearing in London, which took place on 5th and 6th July, Veolia Environmental Services and the council clashed with People Against Incineration (PAIN) campaigners in a bid to overturn a previous High Court judgement which stated that an £850m waste management contract with Nottinghamshire County Council should be made public.

In October last year, High Court judge Mr Justice Cranston ordered details of the company's 2007 contract with the council, as well as numerous monthly invoices and other documents, to be disclosed to Shlomo Dowen from PAIN who has been fighting the application.

The campaigners argue that they should be allowed to view the contract because it is a private finance initiative (PFI) – which means large-scale public service projects can be funded by the private sector.

But Veolia said the information was highly sensitive and commercially valuable - and to disclose it would represent a violation of European and human rights laws.

After hearing the evidence, the judges adjourned the case and they are expected to come to a decision either before the end of the month of after the court's summer recess which finishes at the beginning of October.

PAIN campaigner Mr Dowen, who was represented by a lawyer for Friends of the Earth, said: "Justice Cranston's original judgment, which was clearly the right one, strengthened our right to see how public money is spent buying public services from large corporations.

"I am not convinced that Nottinghamshire Council is getting best value for our money."

In a statement following the hearing, a spokesman for Veolia said: "We first requested a legal ruling on this issue because we wanted to give clarity to local authorities, the general public and the waste management industry.

"It is really important to look at this issue in the wider sense. Making any commercially sensitive material available to a direct competitor could potentially have an adverse effect on the benchmarking process.

"This could mean an increased cost to the local taxpayer and that is something that must be taken very, very seriously."

The spokesman added that Veolia would be able to comment on the situation further once the judges had made a decision.

Meanwhile, Nottinghamshire county councillor Richard Butler, cabinet member for environment and sustainability, said: "The county council works with many contractors and is very sensitive to commercial interest.

"However, as a public body we must ensure that we comply with the law and are open, transparent and accountable to the local taxpayer where we can be.

"We look forward to receiving the Court of Appeal judgment in this matter, having invited the court to provide clarity and guidance on the law so as to ensure that we comply with our statutory obligations."