The advert was found to be in breach of broadcasting guidelines
A television advert about the proposed Greater Manchester congestion charge breached advertising guidelines, broadcasting watchdog Ofcom has ruled.
The advert, funded by the Department for Transport for the Greater Manchester Passenger Executive (GMPTE), cost £230,000 to make and broadcast.
It was deemed biased because it showed a website set up by transport bosses which Ofcom said supported a yes vote.
The watchdog said the advert "directed towards a political end".
The film was taken off air after claims it was biased on Wednesday.
The report published on Friday said Ofcom guidelines "prohibit political advertising".
The Greater Manchester Future Transport (GMFT) website shows how £2.8bn of government funding will be spent if the congestion charge is approved.
The advert, which was aired on ITV Granada, was withdrawn after complaints were made to the broadcasting watchdog.
It was broadcast as 1.9 million voting packs on the charge - and linked public transport improvements - were being sent out to residents ahead of the referendum.
The report added: "The complaints alleged variously that the advertisement was biased towards the 'yes' choice in the poll and constituted propaganda."
Andrew Gwynne MP for Denton and Reddish said: "These publicity materials, paid for by the taxpayer, clearly overstep every boundary in terms of bias.
Let's just get on and vote
"It doesn't matter how much money they throw at this, the vast majority of my constituents know the real damage the C-charge will do to our communities and they also know we get very little of the proposed public transport investment.
"No amount of glossy literature, dodgy websites or skewed TV adverts will convince them otherwise. The ballot must go ahead, and I urge my constituents to vote no."
Lis Phelan, from the Yes campaign, added: "The time has come for everybody to drop this obsession with adverts, websites and the wording of ballot papers.
"This referendum is not being decided by lawyers or watchdogs, but by the mother who needs to get her child to school; the pensioner worried about getting home safely at night, and those who will welcome the chance of 10,000 new jobs. Let's just get on and vote."
Greater Manchester residents must return their votes by 11 December and the results will be announced the following day.
If the proposals get the go-ahead, rush-hour commuters will be charged up to a maximum of £5 a day to drive in and out of Manchester city centre.
In return, the region will receive the £2.8bn public transport investment from the government.
Ofcom revealed the advert had been cleared for broadcast by Clearcast, which examines scripts before they are aired.