Children's minister Beverley Hughes was snared by protester Andrew Tindale as she visited a nursery and primary school conference at G-Mex.
The minister released herself from the toy handcuffs soon after and was unhurt, but the protester was escorted from the venue by security guards without police being called.
Bosses at the venue defended the decision not to report the incident to the police, claiming they believed it was not serious.
A spokesman said: "There was no formal complaint or request for us to involve the police.
"The organisers of the conference did not ask our security to accompany the minister during her visit.
"Our staff did not witness the actual event and, as they did not witness any crime, were unable to make citizen's arrests."
TSL
Special security arrangements for the minister had been declined by the conference's organisers, TSL Education, he said.
The Stretford and Urmston MP had been examining a stall selling hand puppets when Mr Tindale shackled himself to her at around 9.45am yesterday. Mr Tindale, 37, from the north east, who was protesting over a recent custody decision, said he had been preparing for a grilling by police and was surprised when he was released minutes after the incident.
He said: "I phoned my solicitor and they were wondering about what to do with me and finally just let me out of the back door.
"I was prepared and expecting to be arrested because I believe in what I'm doing." Greater Manchester Police said they had not received a complaint about the incident.
A spokesman said: "GMP investigates all reports of alleged crimes it receives. In this instance no one has contacted police about this alleged incident."
Officials at the Department for Education and Skills declined to comment on the minister's security arrangements.
The stunt is the latest in a series of actions against ministers by the protest group.
In February, Education Secretary Ruth Kelly was struck with an egg as she left Salford magistrates' court after attending the case of a protester who had previously targeted her.
And in February 2004, then Children's Minister Margaret Hodge was handcuffed by a protester during a family law conference in Salford.
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A Dad, Manchester (07/05/2006 at 19:43)
They have been waiting 36 years so far and they are not going to wait any longer...
you have been warned!!!!!