Manufacturers used scaremongering tactics to persuade MEPs to vote against banning harmful gases, a politician has complained.
There are more than 15,000 lobbyists canvassing MEPs
Last month saw a key vote over proposals to phase out the substances used in fridges and air conditioning.
Avril Doyle steered the legislation through the European Parliament.
The Irish MEP told File On 4 that her colleagues were sent dozens of letters from industries in their constituencies "threatening them with job losses."
The debate in Brussels about fluorinated and greenhouse "F-Gases" began more than two years ago.
As regulation to control their use in EU countries began to look likely, leading firms such as Du Pont, Mitsubishi and Hitachi employed PR professionals to represent their interests.
"It's been six months of intense lobbying," said Ms Doyle.
"It was email, writing, phoning and faxing, non stop."
She added that MEPs received letters "threatening them with job losses if they voted for this amendment or they voted for that directive."
"Are they really going to vote for legislation that they actually know nothing about - or are they going to take the word of industries based in their constituencies where they have to go back to face election?"
Lobbying is a legitimate part of the democratic system to bring important issues to the attention of politicians.
But, according to Ms Doyle, the F-Gas industry lobby "over-gilded the lily. It was scaremongering."
MEPs rejected calls to impose bans on F-Gases, opting instead for measures to contain and monitor their use.
Ms Doyle believed the legislation was "heavily influenced and directed by lobbyists."
One of Brussels's biggest PR consultancies, Hill and Knowlton, pressed the manufacturers' case.
Speaking to File, lobbyist Mary B Walsh denied that her company over pressurised any MEP.
"I'm very comfortable with the dialogue we had with them.
"It's the premise of business that people should have the right to voice their position with elected representatives.
"I think the companies were worried in terms of what they would have to do in relation to supplying their customers with the goods that they have been asking them for."
EU Commissioner Siim Kallas is currently working on a code of conduct for the lobbying industry.
"It's understandable, because a lot of decisions are made in Brussels, especially concerning business, that there is an interest," he said.
"But obviously these activities have developed to such an extent where this is really noticed by citizens and a certain clarification would bring added value to the picture of how decisions are made in Brussels."
File On 4: BBC Radio 4, Tuesday 22 November, 2005 at 2000 GMT and repeated on Sunday 28 November, 2005 at 1700 GMT.