Lord Blunkett says he does not regret his 2004 decision to open UK borders to east European migrants, which led to a surge in immigration.
The former home secretary told the BBC it was a decision taken to allow people to work legally - not a "failure".
At the time, Labour ministers highlighted a report suggesting 13,000 migrants a year would come, but that proved to be a huge underestimate.
Former minister Jack Straw has said the policy was a "spectacular mistake".
Unlike France and Germany, which did not give migrants from the eight countries which joined the EU in May 2004 full access to their labour market until 2011, the then Labour government did not insist on any transitional controls.
Asked whether he regretted the failure to do so, Lord Blunkett told Radio 4's PM programme: "No, I don't. It was a decision, it wasn't a failure.
"It was a decision to allow people to work legally, openly, transparently, to pay taxes and national insurance and the numbers coming in openly, legally and working are a fraction of those who Germany have taken because they are refugees."
He said the failure was not to "put in place the mechanisms to absorb and to support those people coming in and to support the communities who were hosting them - not the decision to be open and transparent about it".
He added that he did not believe the policy was ultimately responsible for stoking Euroscepticism in the UK.
Lord Green of Deddington, chairman of pressure group Migration Watch UK said: "It is surprising that Lord Blunkett has no regrets about one of the most serious blunders committed by his government.
"They based themselves on a report that predicted a maximum of 13,000 net migration a year.
"We said at the time that this prediction was 'almost worthless'.
"In the event the population of East Europeans increased by nearly a million in the following ten years.
"This had a huge impact on public services and housing in many communities, for which the government failed to provide."
Only the UK, Ireland and Sweden fully opened their borders to nationals of the eight states that joined the EU in May 2004, which included Poland, the Czech Republic, and Hungary.
At the time the government quoted research suggesting the move would increase the UK population by 13,000 a year - although the author of that report has since said it was misinterpreted.
Then Home Office Minister Beverley Hughes told MPs in 2003: "The number coming here for employment will be minimal."
Jack Straw, Mr Blunkett's predecessor as home secretary, has since described the policy as a "spectacular mistake".
He said handing immediate working rights to Poles and others when they joined the EU nine years ago was a "well-intentioned policy we messed up".
Office for National Statistics data suggests that there were 76,000 arrivals to the UK from the eight countries that joined the EU in 2004 in the year to December 2005, 92,000 the following year and 112,000 the year after.
Figures from the University of Oxford's Migration Observatory suggests "net flow" of EU nationals - taking into account people leaving and and arriving in the UK - shot up from 15,000 in 2003 to 87,000 in 2004 and continued to rise until 2007 when it reached 127,000 a year.