Mr Blunkett, who was visiting the National Union of Teachers conference in Blackpool, was released only after pleas from the union general secretary, Doug McAvoy.
Labour's front-bench spokesman last week condemned classroom strikes, and promised to sack incompetent teachers and shut failing schools.
The ugly incident occurred when Mr Blunkett and his guide dog, Lucy, arrived at the Winter Gardens hall. About 30 demonstrators pursued the shaken-looking MP, shouting: "Sack the Tories, not the teachers!"
The menacing chanting continued as conference stewards managed to hustle Mr Blunkett and his dog into a side-room. He was penned inside while about 20 demonstrators chanted: "What do we want? We want to strike! When do we want it? Now!" Some hammered on the door and on a glass partition, apparently trying to get in.
Mr McAvoy was forced to leave the conference platform to plead with demonstrating teachers to return to their seats so that Mr Blunkett could be released.
As the protesters dispersed, one of them, George Arthur, a primary school teacher, said: "I am appalled Mr Blunkett wants to sack teachers in failing schools." Many of the demonstrators wore Socialist Workers' Party badges.
Later, Mr McAvoy said: "This is a sad day for the union. The image of the mob will live with me for a long time." The NUT is investigating the incident and those who took part could be expelled from the union.
After he had regained his composure, Mr Blunkett said: "I think that a handful of people - most of them not teachers - cannot detract from the good relationship between myself and leaders of the NUT, who are committed to raising standards for all our children."
The education spokesman went on to deliver a controversial speech to a conference fringe meeting, in which he once again rounded sharply on teachers threatening to go on strike, arguing that industrial action was "damaging the educational future of children".
In the most forthright condemnation of classroom disruption yet heard from a Labour front-bencher, he declared: "No teacher in our schools can play games with the futures of our children."
On the eve of a critical vote by NUT delegates on industrial action over class sizes, Mr Blunkett said: "No one wants class sizes that make education difficult to deliver and classes impossible to control. But action must not damage the future of the children we seek to protect."
He criticised a recent rash of 24-hour stoppages, including one in his home city of Sheffield, where he was once leader of the council, saying: "As a parent, earlier this month I experienced my children having what they saw as `a day off school'.
"It didn't bring pressure to bear on Government, as most Cabinet ministers don't send their children to state schools, let alone in the areas affected, and it didn't touch those who do not have children in school or were not interested in politics." Mr Blunkett complained: "The only ones affected were the very children whom our teachers seek to protect."
He urged teachers to engage in "clear thinking about co-ordinated action which brings pressure to bear on Government and every Conservative MP" rather than strikes. "We have emerged from years of turmoil, confusion and the misuse of time and money. Now is the moment for rebuilding, not through conflict and division, but to create a united education service capable of helping us build a united and confident Britain."
Earlier, delegates had voted to defy their executive and put forward to the Trades Union Congress in September a motion for a one-day strike by public sector unions over pay. They also voted for a special salary conference in November to discuss strikes.
Mr Blunkett last night admitted that "comprehensive schools are failing a significant minority", but denied that parts of his speech were intended as coded criticism of the Labour leader. He defended Tony Blair's decision to send his 11-year-old son, Euan, to an opted-out stateschool.
Mr Blunkett attacked selection in schools, which some interpreted as an oblique reference to the Labour leader. However, an aide insisted Mr Blunkett had always supported Mr Blair's choice, based on "school religious catchment area".
Last night Tony Blair said he "thoroughly deplored" the treatment of David Blunkett at the NUT conference.
In a move interpreted by some observers as an attempt to avoid divisions in the Labour camp on education, Mr Blair said he strongly supported all the views Mr Blunkett had expressed during the week. "The answer to the crisis in our schools is not strike action," he said.
Labour's policy, page 10Reuse content