The Parliament voted down a draft resolution after it was watered down by an amendment.
According to Bas Eickhout, a Dutch Green MEP and rapporteur for the Parliament's position on EU emissions reduction targets, the vote was distorted by undemocratic lobbyists.
"The German liberals did not follow the group line because of the heavy lobbying from industry," he told EurActiv.
Because the pressure involved "small groups of industrial interests" who did not represent more climate-friendly businesses, it was "absolutely not an act of democracy," he said.
The vote, which was postponed last month, saw a majority of 347-258 against the proposal, with 63 abstentions.
But it only came after Conservative and centre-right MEPs passed a series of wrecking amendments, which forced the Green Party and Social Democrats to vote against it.
BusinessEurope's climate spokesman Folker Franz said he was surprised at the majority against the draft resolution.
"It is no secret that we are against this call for 30% unconditionally, without any movement in international negotiations, but we were not at all active today (5 July)," he told EurActiv.
Franz accepted that his group had sent letters to MEPs in the run-up to the vote, but said that minorities had a right to express their opinion.
"There are a lot of environmental activists running around who don't represent that many people either," he said. "So long as nobody is bullied or pressured I don't see any problem."
Eickhout noted that a "Polish focus" may also have helped sway the vote, a few days after the country took up a six-month tenure as EU president.
"All the Polish MEPs in the Parliament voted against," Eickhout told EurActiv. "They were united across parties."
Less united were Britain's Conservatives, who challenged their prime minister David Cameron's claim to run the "greenest government ever" by rebelling against his support of a 30% emissions cut.
James Holt, a spokesman for the Conservative MEPs in the Parliament, told EurActiv that "Conservative MEPs supported an amendment proposed by the EPP group which proposes moving to a 30% reduction when conditions allow".
There was "no fundamental difference between Conservative MEPs and the government on the substance of the issue," he added.
The vote in Strasbourg may be a source of grim satisfaction for EU Energy Commissioner Günther Oettinger, who has argued that a 30% cut could lead to the "de-industrialisation" of Europe.
A year ago, Climate Action Commissioner Connie Hedegaard initiated the current climate debate when she published data showing that the steep fall in emissions that followed the 2008 financial crisis would make it cheaper to achieve the 30% target than previously thought.
Her department noted that it would also make it substantially easier to meet the EU's objective of reducing emissions by 80-95% by 2050.
The low-carbon roadmap for 2050 approved earlier this year argued that 25% emissions cuts were possible, if the EU's energy savings goals were also met. Hedegaard denied that MEPs had rejected this in their vote.
"While there is still a discussion within the European Parliament about when to move to a 30% reduction, the vote showed that there is a very large majority which supports the idea of going beyond 20% by the EU delivering its own energy-efficiency target," she said in a statement.
Although the call for a 30% CO2 cut fell at the final vote, her department noted that 640 MEPs voted in favour of ammendments supporting a 25% cut in greenhouse gases, or more.