The EU executive is flying six top officials plus an unspecified number of aides to June's Rio Summit on sustainable development but plans to tighten spending, a European Commission spokeswoman said Thursday.

Commission president Jose Manuel Barroso will fly to Brazil with commissioners Janez Potocnik (Environment), Connie Hedegaard (Climate), Andris Piebalgs (Development) Maria Damanaki (Fishing) and Dacian Ciolos (Agriculture), said spokeswoman Pia Ahrenkilde Hansen.

Speaking after the European parliament cancelled its participation due to concerns over cost, the spokeswoman said the commissioners would "be accompanied by collaborators, but the make-up of the delegations isn't yet finalised."

"We're very sensitive to costs and are trying to reduce our expenses as much as possible in all fields including travel and accommodation," she said.

"Only collaborators who have a precise role" to play will go to Rio, she added.

A source speaking on condition of anonymity said however that each commissioner's delegation was expected to number 20 people.

On Wednesday evening, the European parliament cancelled plans to send a delegation of 11 MEPs to the UN Rio+20 summit, citing spiralling hotel costs in particulat.

"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.

He requested parliament formally register a complaint to the organisers 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, who had been due to lead the delegation.