New rules are being drafted to improve transparency in EU institutions, but the intensity of lobbying in the internet age makes the "Brussels gravy train" image hard to shake off.
The anti-corruption organisation Transparency International says about 3,000 lobbying groups have offices in Brussels. It is among a number of watchdog bodies and Euro MPs arguing that tougher EU rules are needed to address conflicts of interest and the influence of powerful lobbyists over European legislation.
At a time of budget cuts and economic austerity across Europe the millions of euros oiling the wheels of EU negotiations are coming under closer scrutiny.
A revised code of conduct for EU commissioners and a joint EU Commission-European Parliament register of lobbyists are likely to be launched this year.
The effort goes some way towards answering the many critics who say Brussels is too remote from ordinary citizens.
The Commissioner for Inter-Institutional Relations, Maros Sefcovic, says he wants the code of conduct to be "one of the best in the world".
"We're beefing up the role of the ethics committee," he said, referring to the small EU panel that vets appointments of ex-commissioners to new jobs.
Many ex-commissioners quickly land lucrative jobs in industry or consultancy after their stint in Brussels - a phenomenon known as "revolving doors".
The ethics panel's "opinions and reasons for their actions" will be published, he told the BBC's Democracy Live website.
But the European Parliament's budgetary control committee has criticised the Commission's plan, saying it does not go far enough.
An influential centre-right MEP on the committee, Ingeborg Graessle from Germany, said the new draft code would still not prevent conflicts of interest - cases where ex-commissioners could earn consultancy fees based on their specialist inside knowledge.
A key element of the code is the "cooling off" period for ex-commissioners - a period during which they are banned from working as lobbyists in their area of EU expertise.
The Commission wants the period to be 18 months. Too short, say the critics. Transparency International and the environmental group Friends of the Earth Europe say it should be three years; the Greens/European Free Alliance MEPs call for two years.
Ms Graessle told the BBC that many EU policy areas overlap - but the new code does not reflect that. "Lobbying elsewhere is still allowed, when it is not in the commissioner's domain. But the Commission is a collegiate institution - they decide everything together," she said.
It is doubtful whether MEPs, whose job it is to scrutinise the Commission's work, will have a full vote on the new code before it takes effect. Ms Graessle voiced frustration at how this "hot potato" was being handled in Brussels, saying her committee had worked hard on it "but they don't rely on our competence - and that's not fair".
The code does not address the controversy surrounding "transitional allowances" - the system whereby ex-commissioners carry on receiving up to 60% of their salary for three years after leaving the Commission.
Commissioners have a basic annual salary of about 248,000 euros (£210,000; $342,000) pre-tax, plus numerous allowances and a generous pension scheme. EU staff - funded by European taxpayers - also enjoy a special income tax rate, lower than the rate in most member states.
Last year former commissioners Lord Mandelson of the UK and Germany's Guenter Verheugen came under media scrutiny over their transitional allowances - paid despite their lucrative new jobs.
According to the think-tank Open Europe, their payments have stopped now, but other ex-commissioners are getting the allowances, including some national politicians - Lithuanian President Dalia Grybauskaite and Italy's Foreign Minister Franco Frattini.
The amount ex-commissioners earn in their new jobs affects the level of the allowance. But Open Europe says they can earn more than 100,000 euros annually while still getting the full allowance.
Despite these "golden parachutes" Open Europe's director Mats Persson said the Commission was at least "slowly moving in the right direction" with the new code of conduct.
Transitional allowances - which also apply to former European Court of Justice judges - are the responsibility of the EU Council, the 27 member states' governments. The Commission could ask the Council to reduce the allowances or simply scrap them, but it does not have to.
Register of lobbyists
MEPs say they would like those who lobby the Council - a key player in EU policy - to join the register too, yet that is only an ambition.
Paul de Clerck, spokesman for Friends of the Earth Europe, says more than half of the lobby groups in Brussels are not on the current public register, and "often the register's data is inaccurate, misleading or out-of-date".
As the register is voluntary, only peer pressure can make lobbyists disclose data, and the financial reporting does not have to meet international accounting standards.
Moreover, the Commission itself has complained that many law firms and think-tanks have not registered.
Mr de Clerck did however welcome a plan to link registration with the issuing of access badges to the European Parliament, so "de facto it will mean the main lobby groups will register".
Badge holders can come and go in the parliament without needing formal invitations for each visit, making their lobbying activities easier.
One of the biggest corporate lobbyists in Brussels, Businesseurope, says it backs the drive for greater transparency.
"It's a good idea to bring in some light," Businesseurope spokesman Christian Feustel told the BBC.
"But don't make it too bureaucratic. Financial data is always sensitive, and you need to define what exactly is meant by 'direct lobbying'," he said.
Businesseurope gives a figure of 550,000-600,000 euros for its lobbying in Brussels in 2010 - a figure that might seem small. But Businesseurope is also an EU "social partner", meaning that it is often invited to represent company bosses at EU meetings and events. The "social partner" activities do not count as lobbying.
Advisory groups - panels of outside experts - have considerable influence over EU legislation, and confidentiality rules generally apply to them.
Mr de Clerck says hundreds of these groups advise the Commission at the early stage of policymaking and he sees a definite bias towards big business.
That complaint was echoed recently by a French liberal MEP, Corinne Lepage, who said "we have highly unbalanced expert groups - lots of big companies, very few SMEs [small and medium-sized enterprises], and the industrial sector but not civil society".