The union, which has around 75,000 members in the telecommunications industry, admitted Labour may have to include the group in the tax net for legal reasons but insisted it had shed most of its utility trappings and should be treated more leniently.
Tony Young, the CWU's joint general secretary, said BT was already tightly regulated and had contributed pounds 8bn to Treasury coffers in corporation tax. He said: "The pragmatic realisation is that there is going to be a windfall tax. BT has been well regulated and consumers have benefited. Those factors ought to have been taken into account by Labour."
The document outlining the union's strategy for the industry urges the next government to remove the ban on BT and Mercury broadcasting entertainment services down their phone wires. It also argues for an end to the ban on BT offering radio technology for fixed phone lines, a system used by the fast-growing phone company Ionica.
Another proposal is to allow BT to buy the 40 per cent of the Cellnet mobile network off its partner, Securicor.