Postal services regulator Postcomm is to be merged into Ofcom.
Postcomm's regulatory responsibility and its staff will be moved to the communications watchdog.
The announcement was made in the Postal Services Bill, which is to be debated by the House of Commons before being considered by the House of Lords.
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Business secretary Vince Cable said the move was necessary to combat Royal Mail's falling mail volumes and multibillion-pound pension deficit.
"This is an important package. It will secure the services that consumers and businesses rely on. It will remove the risk to taxpayers of an expensive bail out," he said.
He added that the network of 11,500 Post Office branches is not for sale and there will be no further programme of closures.