The decision was taken earlier this week by political group coordinators of Parliament's Environment Committee, in light of spiralling hotel costs.
"The huge increase in the estimated cost of attending the summit is simply not justifiable, especially at a time when many Europeans are faced with economic hardship," said Environment Committee Chairman Matthias Groote.
Countries in Rio will be asked this summer to sign up for 10 new sustainable development goals for the planet and promise to build green economies at the first earth summit in 20 years.
Reportedly, they will also be asked to negotiate a new agreement to protect oceans, approve an annual state of the planet report, set up a major world agency for the environment, and appoint a global "ombudsperson", or high commissioner, for future generations.
Some of the main proposals in a draft text for negotiation at a UN sustainable development conference next month are being watered down at informal talks in New York, observers say, heightening fears the summit will fail to deliver.
Dozens of heads of state, political leaders and celebrities are expected to go to the UN's Rio+20 sustainable development meeting.
Groote requested yesterday (9 May) that Parliament formally registers a complaint to the secretary-general of the conference.
"The Brazilian government should have taken action to avoid hotels abusing their position. That's also part of the responsibility of hosting such a large conference." said Parliament's biodiversity and resource efficiency rapporteur Gerben-Jan Gerbrandy (ALDE, NL), who was due to lead the 11-member delegation.
US President Barack Obama and British Prime Minister David Cameron have also said they will not attend the conference. Cameron has said he is not planning to attend Rio+20, despite promising to lead the "greenest government ever" and the date of the summit being changed to avoid a clash with Queen Elizabeth II's diamond jubilee.