The "culture of spin" in the government must come to an end, Constitutional Affairs Minister Harriet Harman says.
Briefing the media first is 'wrong and divisive', says the minister
She said there was "dismay" plans to give police new anti-terror powers to stop and search were released to the press before MPs knew of them.
"We must turn over a new leaf to win back the trust and confidence of the British people," she said.
Ms Harman - a candidate for Labour's deputy leadership - said important plans must first go to parliament.
It was "wrong and divisive" MPs, cabinet ministers and members of ethnic minority communities should learn of government plans through the media, she added.
The proposals to allow police to stop and question anyone in the UK under new anti-terror laws have been criticised, with opponents warning that plans to ask people about their identity and movements may harm community relations.
Northern Ireland Secretary Peter Hain - also in the running for deputy leader - said care must be taken not to alienate whole communities.
But Home Office minister Tony McNulty said there would be plenty of time for consultation.
Organisations representing police and the Muslim community said they were not aware of any consultation before the plans were floated in the press on Sunday.
Ms Harman said: "We must have once and for all an end to briefings and spin.
"Consideration of plans to increase security and counter-terrorism are too important to be handled by way of newspaper briefing.
"We need to build consensus on the difficult issues of how we make this country safe, protect civil liberties and strengthen links with Muslim communities.
Former police minister John Denham - who now chairs the House of Commons Home Affairs Committee - told BBC Radio 4's World at One programme he had not heard senior police officers making a case for this sort of power.
"What does seem surprising is that the government don't seem to have based this on representations and clear, detailed evidence from the police service itself.
"That is what is going to be very important to many politicians and members of the public."