Sir Norman's outspoken attack, which was rejected by Granada, comes as the Independent Television Commission prepares to consider the Conservative complaint over Granada's alleged breach of its broadcasting licence.
The dispute arises from the World in Action programme 'Tory Tax Bombshell' on 28 February, which examined the party's record on taxation against pledges given before the last election. The documentary, seen by nearly eight million people, worked out the new tax bills of three families in southern Kent who had voted Tory.
Some observers see it as a significant first test of the impartiality clause of the 1990 Broadcasting Act.
Sir Norman told Channel 4's Right to Reply programme last night: 'I think we are allowed to make complaints about something which, in my view, is unfair and which is biased and which is bigoted.'
The comments were rejected by World in Action's executive producer, Charles Tremayne, who said Granada had no intention of climbing down. 'We don't believe that the programme was either biased or broke the 'due impartiality' guidelines of the Independent Television Commission,' he said.
'Surely taxation is a matter of serious public interest. We have a party that was elected on the promise to reduce taxes and for whatever reason has decided to put taxes up. We decided to have a look at that issue.
'I think the programme was very fair to the Conservative Party. The Conservative Party were invited on, the Treasury ministers were invited on, and unfortunately they chose not to take part'. He added that 'not one of them, when they refused, said that the question of bias was an issue'.
This month Sir Norman wrote to the ITC: 'The clear purpose and intention of the programme was to undermine support for the Conservative Party. The title and graphics used by the programme are identical to recent material issued by the Labour Party.'Reuse content