Business Secretary Peter Mandelson said:
"I very much regret this decision by the CWU. Candidly, I think it is suicidal. Taking industrial action will not resolve this dispute.
"It will only serve to drive more customers away from Royal Mail. One thing this company cannot afford is strikes and industrial action.
"We are, of course, in frequent contact with both management and the union. Our message to them has been clear: put your customers first.
"The CWU should turn their backs on industrial action and sit down with the Royal Mail and resolve this dispute. That is what is in the interests of the Royal Mail, their members and the country."
Notes to editors
Department for Business, Innovation & Skills
The Department for Business, Innovation and Skills (BIS) is building a dynamic and competitive UK economy by: creating the conditions for business success; promoting innovation, enterprise and science; and giving everyone the skills and opportunities to succeed. To achieve this it will foster world-class universities and promote an open global economy. BIS - Investing in our future.