Postal workers will stage a protest outside Parliament today ahead of an appearance by the Business Secretary before a committee of MPs over the controversial privatisation of the Royal Mail.
Activists will dress up as highway robbers, carrying banners saying "The Great British Royal Mail Robbery" to mark Vince Cable's session before the Business, Innovation and Skills Committee.
The minister will face questions on the valuation of Royal Mail, including whether it has been undervalued by the Government; d etails of the employee share scheme; p rotection of the universal service; and the v alue of company assets, including the Nine Elms site in south London.
The meeting will be held following the deadline for buying shares, at midnight last night, with conditional trading starting on Friday and full trading next Tuesday, a day before the result of a strike ballot by the Communication Workers Union.
Labour and the unions have warned the Government it is selling the postal operator too cheaply, amid predictions of huge profits by investors.
It is believed that 368 of the Royal Mail's 150,000 staff have chosen not to accept free shares in the privatised company.
The CWU said it had never told its members not to accept the shares, which could be worth about £2,000, adding that it did not mean they agreed with the privatisation.
CWU members are expected to back industrial action over issues linked to privatisation, with any strike set to be held on or after October 23 - the run-up to the busy Christmas period.
Mr Cable has warned Labour that its opposition to the sale was "irresponsible", adding it was "dangerous" to imply there was an easy bargain to be made.
He told his Labour counterpart Chuka Umunna that he was magnifying a small minority of views which take a "short-term view" of the flotation.
Mr Umunna said: "It's a dream for City speculators and hedge funds, but it's a nightmare for the taxpayer, who ultimately doesn't want this to happen anyway and is now being hugely short-changed."
Billy Hayes, general secretary of the CWU, said: "It's no surprise that the Government has sold the postal service cheap to its friends in the City.
"The public didn't want the service sold and will get a worse service as customers. Now they also know they are getting a bad deal as taxpayers too."
Mr Cable wrote to Mr Umunna, saying that value for money for the taxpayer was an "absolutely key consideration" and adding that Labour's line on the sell-off was "irresponsible".
He wrote: "Getting the right price in the transaction is in the interest of taxpayers, consumers and employees alike, as is ensuring that ownership of the Royal Mail moves smoothly to responsible investors able to take a long-term, responsible approach to owning the company.
"The approach we are taking encompasses all of these considerations.
"I worry that the line you are taking on the other hand is irresponsible, simply magnifying a small minority of views which take a short-term view of the flotation.
"To achieve value for the taxpayer, we set the price range based on extensive consultation with investors.
"We have also undertaken a market standard 'book building' exercise during which the management have been communicating to investors the key highlights of the business and its future potential.
"This process should ensure that the price paid by investors appropriately reflects the value of the business, while creating an enduring shareholder base amongst long-term institutional investors and positive aftermarket performance over the long term.
"I also feel it is irresponsible to imply that a share offering looks significantly undervalued.
"I think you should consider the risk that you may be influencing the decisions of retail investors. Equity investment always involves risk, particularly when the company in question is new to the market. In the light of this, it is dangerous to imply that there is an easy bargain to be made."
Mr Umunna has urged the Government to pull the plug on the privatisation to prevent a "massive bonanza" for City speculators.