Rumiana Jeleva evidence session: From BBC Democracy Live
Bulgaria's nominee to the new European Commission has resigned - a move that could delay confirmation of the new 27-strong team.
Rumiana Jeleva's move followed tough questioning from Euro MPs about her financial interests.
Last week doubts were expressed about her competence for the role of EU commissioner for humanitarian aid.
Kristalina Georgieva, vice-president of the World Bank, has been put forward as the new Bulgarian candidate.
Ms Jeleva's resignation came in a letter to Bulgarian Prime Minister Boiko Borisov, Reuters news agency reports. She had also been serving as Bulgaria's foreign minister.
MEPs can veto the whole Commission if they oppose one of its members.
The row over her candidacy centred on her past management of a consultancy firm. She denied any wrongdoing.
Ms Georgieva has held senior positions as an economist at the World Bank
A Bulgarian liberal MEP, Antonyia Parvanova, disputed Ms Jeleva's declaration that she had ended her involvement with the Bulgarian firm Global Consult in 2007.
Ms Parvanova claims she was still managing the company until 2009.
Any undeclared financial interest would put Ms Jeleva in breach of European Union rules.
The European Parliament's legal service cleared her of wrongdoing, but MEPs also doubted her competence.
Her resignation sparked an angry reaction from her centre-right political allies in the parliament, the BBC's Dominic Hughes reports from Strasbourg.
The head of the European People's Party (EPP), Joseph Daul, said she was "the victim of a contemptible political squabble". The EPP is the biggest grouping in the parliament.
But the leader of the UK Labour MEPs, Glenis Willmott, said "common sense has prevailed".
"The issue was her competence. She did not give a good account of herself at the hearing."
It is still possible that other would-be commissioners could get caught up in the parliament's political in-fighting, our correspondent says.
MEPs are expected to vote on 26 January on the new Commission line-up - but that might now be put back. The commissioners, who have a five-year mandate, cannot take office without the MEPs' approval.
The new Bulgarian nominee, Ms Georgieva, has been World Bank vice president since March 2008. She joined the bank in 1993 and specialised in environmental issues.
She was the bank's director for environment in 2000-2004, and in 2004-2007 she oversaw the bank's projects in Russia.