David Cameron's nomination of Lord Hill to represent Britain on the EU commission has been branded a "shambles" after he had to sell shares in a lobbying firm to avoid criticism over conflicts of interest.
The peer is acting to head off concerns over his significant holding in £140 million global public affairs company Huntsworth, which operates in Brussels.
MEPs had warned that they would be looking closely at the interest in deciding whether to confirm his appointment.
Downing Street signalled the move as the Prime Minister struggled to secure a senior role for the former Leader of the House of Lords in Jean-Claude Juncker's new European Commission.
Mr Cameron is pushing the case for Britain to get one of a handful of economic portfolios - such as trade, internal market or competition - at a summit of EU leaders in Brussels tonight.
However, Mr Juncker is reported to have had to Google Lord Hill - best known in Westminster for unsuccessfully trying to resign as education minister during Mr Cameron's 2012 reshuffle - to find out who he is.
And the president of the European Parliament Martin Schulz suggested that he could be rejected by MEPs for being too eurosceptic - although he later stressed he did not know Lord Hill's views.
"I can't imagine that Hill, with his radical anti-European views, which he is supposed to have, will get a majority in the European Parliament," he told told German radio.
"It remains to be seen whether Mr Hill is unprejudiced towards us, and on that will depend whether he gets a majority," he said.
However, Mr Shultz later rowed back on his comments, telling a press conference: "I have now been informed that he was head of private office under John Major and that he has been able to build consensus within the House of Lords. Friends have also informed me today that Mr Hill is in fact more pro-european than anything else in the UK context, and I'm glad to hear that."
Number 10 pointed out that the European Parliament has the opportunity to approve or reject a new Commission "as a whole, as a slate, not as individuals". Lord Hill told journalists in Brussels he would not view himself as a eurosceptic.
" I'm not a great one for looking for names or badges or boxes. I think I have a pretty straightforward view which is that we need to make reform in Europe and one should want to make reform in Europe if you want to make Europe stronger and make it better for the people of Europe."
He insisted reform was "achievable".
"From my time working in government 20 years ago up until more recently, when people say it's not possible to reform, actually successive periods of time there have been big reforms in Europe.
"So yes, I am optimistic about reform."
Lord Hill previously replied "non non non" when asked if he wanted the EU job - but denied he was a "reluctant conscript".
"I am not a reluctant conscript. It is true that I loved my time at the House of Lords, which is a fantastic institution, full of wonderful people," he said.
"The fact is, having thought about the importance of this job, the pivotal role that it will play, the crucial time in the history of the European Union and also of Britain, it is a fantastic opportunity to be involved and I would be mad not to do it."
Speaking at Prime Minister's Questions in the Commons earlier, Mr Cameron insisted: "I think there is an opportunity to make sure that Britain has an important portfolio, one where we can maximise our influence in the areas that we care about most - and those are areas to do with our economy - and we will look and work very hard to do that.
"I think that Lord Hill, with his experience in the previous Conservative government and in this Government, holding as it is the equivalent post that Baroness Ashton held before she became a Commissioner, will do a very good job for our country."
Lord Hill declares his shareholding in Huntsworth - which dates from when it bought his firm Quillier in 2006 - on the parliamentary register, meaning it is worth at least £50,000. The total value is not clear, although the value of the company's shares has dropped from over 70p to 43p over the past three months.
The process of divesting the holding began today, according to Number 10 sources.
Philippe Lamberts, the leader of the Green bloc, is reported to have indicated that Lord Hill would get a rough ride in confirmation hearings. "Someone with a past in lobbying can expect to be grilled with double the energy," he said.
"We want to reduce the influence of lobbying and we do not want to let the wolves into the sheep fold."
The allocation of portfolios is set to be the topic of fraught negotiation between national leaders and the president at the EU Council meeting tonight, and they are unlikely to agree the full slate.
Each of the 28 member states nominates someone to serve as a commissioner for a four-year term, with Luxembourg's spot already taken up by Mr Juncker.
Britain's current commissioner, Baroness Ashton, has a senior role as High Representative, which means that brief will go elsewhere this time round.
The summit could agree a president of the European Council to succeed Herman Van Rompuy - with Danish PM Helle Thorning-Schmidt, wife of Neil Kinnock's son Stephen, thought to be in the running.
There had been speculation that Mr Cameron would nominate former Tory leader Lord Howard or former Leader of the Commons Andrew Lansley for the UK's spot on the Commission before Lord Hill was given the nod.
Mr Cameron is due to have one-to-one talks with Mr Juncker in Brussels tomorrow morning, with Number 10 sources indicating the PM will press the need for reform.
As his appointment as president was rubber-stamped by MEPs yesterday, Mr Juncker again insisted he was ready to accommodate British demands to renegotiate aspects of its relationship with the EU.
But he stressed that the principle of free movement of labour within the union was not up for debate - and signalled his desire to push forward social measures such as a single minimum wage.
Shadow Europe Minister Gareth Thomas described the nomination of Lord Hill as a "shambles".
It comes after Mr Cameron was condemned for failing to give his successor as Leader of the Lords, Baroness Stowell, the status of a full Cabinet member.
She was also originally due to be paid at a lower rate, but the Conservative Party hastily announced it would be topping up her salary.
Mr Thomas said: "David Cameron's approach to Europe goes from bad to worse.
"After his complete failure to stop Jean-Claude Juncker becoming Commission president this shambles will not help in rebuilding our influence to secure crucial reforms."
Ukip leader Nigel Farage accused Mr Schulz of "declaring war" by criticising the British nomination for commissioner.
"This is a declaration of war by Schulz on the choice of the British Government," he said. "How dare Martin Schulz interfere in the British nomination of European Commissioner and prejudge what the decision of the MEPs will be.
"He is supposed to an independent chairman, but he has demonstrated absolutely no respect for national democracy or national government.
"And where he even gets the idea that Jonathan Hill is a eurosceptic is completely beyond me."
:: Mr Cameron gave German chancellor Angela Merkel a bottle of House of Commons whisky to mark her 60th birthday tomorrow, Downing Street said.