The workers union has issued Royal Mail an ultimatum that strikes could begin as early as next Thursday (22 October), if an agreement cannot be reached.
In an open letter to Royal Mail managing director Mark Higson, the CWU's Dave Ward made a "fresh offer" to avoid the planned strikes, with the union set to serve the relevant seven day notice to announce the action on 15 October.
However, Mandelson said that a national postal strike "defies logic" and was a move that would help to turn both consumers and businesses away from using mail.
He said: "The government has backed Royal Mail financially with billions of pounds so that the company can modernise, but these strikes will impede that essential process.
"We remain in close contact with the union and Royal Mail management and our message is clear – strikes are not the way to resolve differences or safeguard the future of our postal services."
Mandelson brands CWU strike action a 'suicidal act' for mail industry
Business Secretary Lord Mandelson has condemned strike action by Royal Mail CWU members as a "suicidal act" that "defies logic" and one that could turn customers away from the mail medium.
