Justice secretary Jack Straw has outlined to MPs today details of emergency legislation allowing witnesses to remain anonymous in some criminal trials.
Last week, law lords ruled that defendants needed to be aware of who was testifying against them.
The ruling led to a £6 million Old Bailey trial being halted on Tuesday.
On Thursday, Mr Straw told MPs in a statement that the use of anonymous evidence was fundamental in some court cases.
The justice secretary added that the reality of witness intimidation must always be taken into account.
He admitted to MPs that the bill was being drafted as he spoke and that his statement today was simply an opportunity to outline the government's thinking.
"Parliament should not legislate at the speed I'm proposing unless there are overwhelming reasons to do so," Mr Straw warned.
The criminal prosecution service (CPS) is said to be looking at the number of cases due to be affected by the Lords decision.
Mr Straw attempted to reassure those concerned by the law lords decision that criminals sentenced by the use of anonymous evidence would not have their sentence simply quashed because of a "technical default in the law".
Earlier this week, Metropolitan police announced that it was "very concerned" with the ruling and the potential impact it may have on future trials.
On Tuesday, home secretary Jacqui Smith admitted the current situation was "a problem we need to solve".
She said Britain needed a legal system in which "yes defendants rights are protected, but also rights of people taking part in trials also protected".