THE HARBOUR company Forth Ports has been accused of trying to hamper an environmental assessment of controversial plans for pumping millions of tonnes of oil between tankers in the Firth of Forth.

The company has been "very heavy-handed", according to the government's conservation agency, Scottish Natural Heritage (SNH). Strict secrecy rules it wanted to impose on SNH officials could have prevented them from advising ministers.

Forth Ports has been backing a plan to transfer Russian crude oil into ocean-going supertankers anchored four miles off the Fife coast. SNH, along with communities and councils around the Forth, has been opposing the plans because of the risks of spillages.

Tense and deteriorating relations between Forth Ports and SNH are revealed in a dossier of correspondence released under freedom of information legislation. The dossier was requested from SNH before the election by the Scottish Nationalist MSP, Bruce Crawford, who is now the minister for parliamentary business.

The SNP has promised to find a way of enabling ministers to block the ship-to-ship plans, though it is not yet clear how this will be done. An announcement is expected in the next two weeks.

Emails between Forth Ports and SNH over the past two years disclose a series of escalating disputes. The company was repeatedly accused by SNH of failing to understand the legislation governing environmental protection, while SNH was attacked for using "highly emotive" language.

The disputes culminated in a clash over arrangements for allowing SNH officials to comment on a draft environmental assessment, known as an Appropriate Assessment under the EU Habitats Directive, being drawn up by Forth Ports. The company wanted SNH to sign a strict confidentiality agreement, but SNH refused.

In an email to the Scottish Executive on January 11, SNH's area manager Iain Rennick was very critical of the way in which Forth Ports had behaved. "Their approach in dealing with us has been very heavy-handed," he wrote.

This could "be perceived by others as constraining our ability to give our advice - whether to them or to Scottish ministers," he added. "In effect they are attempting to transfer difficulties which they have on to us."

Forth Ports told SNH that the then environment minister, Ross Finnie, had agreed to the confidentiality procedure. But this was denied last week by Finnie, who said he had merely agreed to consider the matter.

SNH said that in the end it was given access to Forth Ports' draft assessment without signing the confidentiality agreement. It has made comments on the assessment and is now waiting to hear back from the harbour company.

Forth Ports chief executive Charles Hammond dismissed arguments with SNH as "a storm in a teacup". All the company had been doing was following normal rules of commercial confidentiality to protect shareholders, he said.

"It was resolved and agreed and we moved on," he added. He promised that the final assessment would be published and consulted on "later this year" before any decision was taken.

Labour's former environment minister, Rhona Brankin, suggested that the harbour company had not always been as helpful as it ought to be. "It was felt necessary to emphasise to Forth Ports on several occasions that there was widespread concern about these plans and they should be as open and transparent as possible," she said.

Brankin is pressing the environment minister, Richard Lochhead, to seek an assurance from Forth Ports that it will not proceed with the plans until it has given further evidence to the Scottish parliament's environment and rural affairs committee.

The email dossier discloses frustration within Forth Ports at the government's failure to come to a quick decision on ship-to-ship oil in 2005. "It is unacceptable for government departments to be taking this much time to make one decision," wrote the company's chief harbour master, Bob Baker.

He told the Department of Transport: "It is also quite unacceptable to keep deferring the blame' for the delay on other departments."