Peter Mandelson's appointment as the UK's next European commissioner has met with a mixed reaction in Westminster.
Mr Mandelson denies being a divisive figure
The Tories say he is too pro-European to fight Britain's corner effectively and his political track record means he cannot be trusted.
Labour backbenchers have also hit out at the appointment, with one branding it an "appalling" example of cronyism that would backfire on the government.
But the Liberal Democrats welcomed the appointment of a fellow pro-European.
Mr Mandelson was also backed by former Europe Minister Keith Vaz, who said Britain needed a "big hitter" rather than a faceless bureaucrat to fight its corner in Europe.
"It is important that someone who is of the calibre of Peter Mandelson should be there," he added.
Dari Taylor, Labour MP for Stockton South, next door to Mr Mandelson's Hartlepool constituency, said he was a "very capable politician" who "should be centre stage".
Conservative former vice-president of the European Commission Lord Brittan said that even though Mr Mandelson had "many political enemies" he was well qualified for his new job and had the benefit of a close relationship with prime minister Tony Blair.
But Tory co-party chairman Dr Liam Fox said that in choosing Mr Mandelson, Mr Blair had put his friends above the interest of the country.
"Peter Mandelson will never stand up for the interests of Britain in Europe
because he has always argued the case for Europe in Britain.
"The EU needs commissioners who will actually tackle the appalling problem of fraud and corruption in the EU.
"Peter Mandelson is unlikely to inspire public confidence in their ability to deal with this problem," he added.
He also questioned whether someone with Mr Mandelson's track record - he has twice resigned from the cabinet in controversial circumstances - could be trusted in such an important role.
Liberal Democrat campaigns chief Lord Rennard welcomed the appointment of a pro-European to the job, but said the Hartlepool MP was a "hate figure" within his party.
The appointment would do little to "restore trust" in the Labour government, he said, predicting the Lib Dems would be successful in overturning Mr Mandelson's 14,500 majority in Hartlepool
Many backbenchers have responded with allegations of cronyism.
Glasgow Pollok MP Ian Davidson, of lobby group Labour against a European Superstate, described the appointment as "appalling".
"This will be seen as an example of arrogance by New Labour, bringing in somebody twice resigned, seen as a crony of the prime minister, deeply unpopular in the Labour Party," he told Today.
John Cryer, the Labour MP for Hornchurch, added: "This is not going to help
their campaign for the Constitution - the embodiment of New Labour leading the 'yes' campaign is going to pile up the votes for those who are going to oppose
Kate Hoey, Labour MP for Vauxhall, said: "Peter represents the things people don't like about Europe - he reminds people why they plan to vote no. This is a setback for the `yes' camp".
UKIP MEP, Robert Kilroy-Silk, who is widely expected to stand in the by-election caused by Mr Mandelson's move to Brussels, said: "This appointment of Mandelson shows that the European Union is a gravy train for failed politicians."