The Government was today accused of planning to "demolish" the Royal Mail ahead of the first debate in Parliament of its controversial privatisation plans.
The Postal Services Bill will receive its second reading tomorrow, giving MPs the first chance to question ministers about privatising the Royal Mail.
Postal workers from across the country will meet their MP in the Commons ahead of the debate and will explain why the Communication Workers Union will oppose the move.
Billy Hayes, the union's general secretary, said: "The Government has left many questions unanswered and scrutiny of their Bill shows they are making empty promises while setting up to demolish the mail through the back door.
"Their warm words about keeping post offices open have no substance as the government has not confirmed any funding to keep the network running beyond next year.
"Of serious concern is the small print of the Bill which shows the universal service will be reviewed within 18 months, meaning any promises of six-day deliveries or single stamp prices are worthless.
"These get-out clauses will be attractive to buyers not interested in maintaining service levels but disastrous to consumers, who have just lost their watchdog to the quango bonfire.
"The Government is refusing to explore business models other than privatisation and leaving gaping holes in its legislation which could lead to the decimation of the UK's postal service."
Business Secretary Vince Cable said earlier this month that private buyers will be allowed to own up to 90% of the Royal Mail, with at least 10% of shares going to employees, while the Post Office may be mutualised.
The staff share scheme would be the biggest of its kind - larger than those of British Telecom, British Gas or British Airways, he said.
The Government also announced it would take on the Royal Mail's multi billion-pound pension shortfall as part of its plans.
The union published an opinion poll earlier this month showing that half of voters thought postal services would get worse under privatisation, with 25% believing they would improve.