The government is attempting to create a "society of institutional intolerance", a leading barrister says.
Mr Blair said 'law-abiding people' should live in safety
Michael Mansfield QC told BBC Radio 4's Today programme that measures such as anti-social behaviour orders (Asbos) could "dilute" the rule of law.
In his speech to the Labour Party conference on Tuesday, Tony Blair said he had been "battering" the justice system to ensure the right to safety.
But Mr Mansfield said the presumption of innocence in law was at risk.
He added: "The balance has already been struck many times both by articles in the United Nations charter and the European Convention on Human Rights.
"What he [Mr Blair] is doing is paying lip service to these and deluding people into believing that it's the criminal justice system that somehow or another undermines the cohesion on society."
Asbos did not require the normal "burden of proof" needed to secure a criminal conviction, he added.
The orders, according to the Home Office, are designed to protect the public from behaviour "likely to cause harassment, alarm or distress".
Local authorities and police can apply for Asbos, which are issued by civil courts, allowing the use of "hearsay" as evidence.
They ban certain "anti-social acts" and forbid people to return to areas where they have already "caused problems".
Breaching them is a criminal offence.
Opponents say Asbos, which last for a minimum of two years, undermine fairness and the presumption of innocence in law.
Supporters say they protect communities from bad behaviour, particularly by youths.
Mr Mansfield said: "What we are doing is criminalising a whole section of youth."
In his speech, Mr Blair said: "The whole of our system starts from the proposition that its duty is to protect the innocent from being wrongly convicted.
"Don't misunderstand me. That must be the duty of any criminal justice system.
"But surely our primary duty must be to allow law-abiding people to live in safety."
However, Mr Mansfield said this had gone too far, with the detention without trial of terrorism suspects another problem.
There was no "need to dilute the principles that at the heart of rule of law", he added.