A new and comprehensive raft of data has shed some light on the murky world of European Union lobbyists, revealing that tobacco giant Philip Morris International is the company that spent the most money lobbying EU politicians in 2013.

The Switzerland-domiciled but U.S.-based company spent €5.25 million ($6.7 million) on lobbying over the course of the year during which the European Parliament progressed towards the Tobacco Products Directive – legislation designed to cut the number of smokers in the union by 2.4 million.

That Philip Morris boosted its lobbying budget from €1.25 million ($1.6 million) to more than €5 million ($6.3 million) over the year shows the opposition the bill faced among the tobacco industry, which accused European policymakers of adopting a "nanny state mentality" towards smokers.

The directive was subsequently voted in by the European Parliament in February of 2014 and will lead to picture warnings covering 65 percent of cigarette packets; a ban on smaller cigarette packs aimed at women; a ban on flavored cigarettes; and a maximum nicotine-concentration level in e-cigarettes.

The data comes in the same week that Australian media reported Philip Morris donated "tens of thousands" to an Australian senator who lobbied for smokers' rights and who vehemently opposed plain packaging for cigarettes.

Reacting to the news, Liberal Democrat Senator David Leyonhjelm said: "We are very pleased to receive the donations and we hope to receive them from the other tobacco companies," the Brisbane Times reported.

The EU figures, compiled by Lobby Facts, a coalition of the non-governmental oranizations Friends of the Earth Europe, the Corporate Europe Observatory, and LobbyControl, show petrochemicals behemoth ExxonMobil was a close second in the spending stakes with €5 million ($6.3 million), while Microsoft rounded off an all-American top three with €4.75 million ($6 million) spent over the course of 2013.

European companies Shell, Siemens and GDF Suez follow, with General Electric, Huawei, Bayer and Telekom Austria Group completed the top 10.

The data is based on statistics from the EU lobby register, to which signatures are submitted voluntarily. Lobby Facts points out the likes of Goldman Sachs and Time Warner failed to sign up to the register. Its creators said it offered the public a more user-friendly snapshot of the European lobby system than the cumbersome official tool.

Among trade associations, the Association for Financial Markets in Europe, a UK-based organization that represents the interests of the financial services sector, spent €10m on 50 lobbyists, five of which had EU parliamentary access.

The organization’s list of goals include "promoting the adoption of market-led solutions, standards and practices" and "to co-operate and engage constructively with stakeholders and policymakers toward ensuring open European and global markets that benefit from well-crafted, globally consistent regulations".

But it is the heavy spend of tobacco firms that resonates most strongly, given the contentious recent history the industry has in the European Parliament. In 2012, Maltese politician John Dalli was forced to step down as the EU's Health Commissioner after allegedly demanding €60m ($76 million) from Swedish tobacco company Match in exchange for assistance in altering European tobacco regulations.

The debate continues to rumble on, with the EU being accused in July of failing to keep sufficiently transparent records of meetings between the tobacco industry and politicians. Campaigners have urged the European Commission to adopt the World Health Organization's standards on tobacco control, which necessitates a fully accessible online record of such contact.

The wider data showed lobbyists hold more than 670 European Parliament access passes, with 130 lobbyists accredited between the top five biggest lobby firms (Fleishman-Hillard, Burson-Marsteller, G Plus, FTI Consulting and APCO Worldwide).

More U.S.-based lobbyists appear on the register than Swedish, Austrian, Poland, or Danish, showing the vital importance placed on the EU market by U.S. companies – particularly as negotiations over the Transatlantic Trade and Investment Partnership (TTIP – the free trade agreement between the EU and U.S.) continue.

NGOs have called on European officials to use the new data as an excuse to change the lobbying system and to introduce an obligatory register.

"LobbyFacts further makes the case for an urgent transition to a mandatory register with reliable information. We are pleased with Jean-Claude Juncker's signal in favor of mandatory lobby registration and we look forward to seeing his proposal for a new mandatory EU lobby register promptly after he takes office," said Max Bank, of LobbyControl.

Erik Wesselius, of Corporate Europe Observatory, added: "Lobbying is big business in the EU. We hope that LobbyFacts will become a really useful tool for journalists and activists analyzing and exposing EU lobbying.

"The official lobby register is not very user-friendly or flexible but LobbyFacts enables people to compare lobby data from different lobbying organizations and different countries and to do so quickly."