A blacklist in the construction industry was discovered in March
The government is to introduce regulations to outlaw secret blacklists that stop union members getting jobs.
In March, construction companies were accused of subscribing to a database with details of workers' trade union activity and employment history.
That blacklist was suspended under existing data protection laws but the government wants specific regulations to make prosecutions easier.
It had considered bringing in such laws as early as 2003.
At the time, no action was taken because no hard evidence could be found that secret blacklists were being used.
But earlier this year, the information commissioner said a firm called the Consulting Association had been flagging up workers who had raised safety concerns or who had union links.
"There is already legal protection against the misuse of people's personal details," said Business Secretary Lord Mandelson.
"We now plan to strengthen the law by introducing new regulations to outlaw the compilation, dissemination and use of blacklists in this way."
A consultation process will begin in June. The government hopes new regulations will go to Parliament for approval in October or November and be introduced shortly after that.
Brendan Barber, general secretary of the TUC, welcomed the government's announcement.
"It is outrageous that unscrupulous employers have been victimising trade unionists through shady blacklisting practices that have no place in a democratic society," he said.