The extra 11 days will allow consumer postal watchdog Postwatch longer to speak to customers about the effects the changes to the proposals are expected to have.
Postwatch chairman Peter Carr said: "Postwatch needs as much time as possible to be able to gather feedback from its regional committees and networks, as well as the mailing industry, in order to better understand how the customers will be affected."
Postcomm first launched a consultation period to allow the industry to react to its proposals for new prices and a new compensation scheme between October and December.
It then published its final proposals on February 7, which contained several changes. The latest consultation period had originally been set to end on March 10.
Postcomm's proposals include the introduction of size-based pricing, which would see direct mail packs charged on their size as well as weight. There are concerns that this will limit creativity in direct mail because the cost of mailing larger-than-average envelopes would rise.
The proposals will also see the price of a stamp rise by 1p from April 1. Postcomm believes the deadline extension still leaves it enough time to implement the price rise on this date.
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