The Government has been accused of "dragging its feet" over cracking down on dangerous dogs ahead of an expected announcement of action to tackle the problem of attacks by violent animals.
Millions of dog owners will have to pay for their pets to be fitted with a microchip, under plans set to be announced on Monday.
Ministers are expected to say that every newborn puppy should be fitted with a device giving details of who it belongs to.
An announcement is also expected on closing a loophole in the law so that dog owners will face prosecution if their pet attacks someone in their home.
The postal workers' union said action is "long overdue", pointing out that more than 10,000 people have signed an e-petition supporting changes to the law.
Billy Hayes, general secretary of the Communication Workers Union, said: "It's about time the law bit back to protect innocent dog attack victims. Thousands of postal workers and telecom engineers - along with other workers who go on to private property and parents of small children - will sigh in relief at this announcement.
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"We warmly welcome new laws and hope they will make the improvements desperately needed to the failed Dangerous Dogs Act.
"Government action is well overdue and unfortunately thousands of people have suffered debilitating injuries while the Government has dragged its feet.
"CWU has been calling for the law to apply on private property for years and we fully back compulsory microchipping to identify the owners of dogs and encourage more responsible dog ownership."
The union released details at its annual conference in Bournemouth yesterday showing that 70% of the dog attacks on CWU members happened on private property where the law currently does not apply - effectively treating postal delivery workers and others as "criminal trespassers.
An official said: "The same goes for gas, water and electricity workers, district nurses, home helps, health visitors, care workers and even meals on wheels volunteers, who are all left utterly unprotected by the law because of this weakness in legislation."
More than 23,000 postal workers have been attacked by dogs over the past four years, thousands causing injuries.
Almost 400 postmen and women have taken time off sick in the past year after being attacked by dogs on their delivery rounds.
A number of organisations, including animal charities, have been campaigning for years for changes to the law to tackle dangerous dogs.