The measures - the first significant change to libel law in 50 years - will allow some cases to be settled without a jury and are certain to cut the size of damages.
Lord Mackay believes the package will reduce the expense and complexity of libel actions, helping plaintiffs more interested in restoring their reputation than winning large sums of money.
Under a new summary procedure, proposed by Lord Justice Hoffman and adopted by the Government, minor actions can be settled by a High Court judge who will assess damages up to a fixed ceiling, probably about pounds 5,000.
Another change will allow a defendant, such as a newspaper, to cut short proceedings by admitting a libel but maintaining that it was published as an innocent mistake. Again, damages would be assessed by the judge, but would probably be small. In such cases, known as an Offer of Amends, a plaintiff would have to show that the defendants knew the words to be defamatory, or published them recklessly.
'The Offer of Amends defence will provide a benefit to defendants in particular, while the summary procedure would offer a counter-balancing benefit to plaintiffs,' the Lord Chancellor said.
Both measures will cut out some of the six-figure damages awards made by juries, as well as curbing legal costs of hundreds of thousands of pounds.
Under the reforms, judges will be given powers to determine the meaning of words at the centre of libel cases. At the moment, this is left to juries. The time limit for bringing defamation claims will also be reduced from three years to one.
In a further reform, defendants will be allowed to put before juries evidence that the plaintiff is disreputable and does not deserve damages.
The Lord Chancellor's statement follows a report drawn up by a committee under the chairmanship of Lord Justice Neill who was asked to 'look at ways of reducing the complexity of the procedure' in libel cases. Many of the measures announced by Government were recommended by the committee, although one - urging the creation of a voluntary arbitration system - appears to have been ignored by Lord Mackay.
Some of the reforms can be introduced by amending the rules of court, others will require legislation, Lord Mackay says in a parliamentary answer.
The reforms were welcomed last night by Julie Scott-Bayfield, a libel lawyer. 'They are all to be welcomed and go some way towards correcting what was wrong.'
However, she said that judges should set the level of damages in all cases.