However, it admitted that only a fraction of the costs would ever be recovered. In addition, the Forum of Private Business (FPB) is concerned that employers could be forced to pay for the increased cost of their staff travelling to and from work.

A spokesman for the Yes Campaign suggested that, because roads would become less congested, business-owners would be able to fit in additional jobs to pay for the congestion charge.

"Plumbers will be able to claim back 40% of a congestion charge in tax, so the very most they could pay is £3 a day," said the spokesperson. "With clearer roads, a plumber who charges an average of £50 an hour and fits in one extra hour of work [each week] will be able to pay the charge and still be £35 a week better off."

In June 2008, the Government accepted a bid from the Association of Greater Manchester Authorities (AGMA) for £1.5 billion in Transport Innovation Funds (TIF), which will be used to implement the charge and pay for improvements to public transport. AGMA will have to raise an additional £1.2 billion via the charge for new bus, rail, tram and cycle links.

The Forum of Private Business (FPB) is campaigning against the introduction of the tax, following the serious impact that congestion charging has had on small businesses in London. The FPB's Director of Finance, Nick Palin, responded to the Manchester Yes Campaign's statement.

"Dismissing legitimate concerns about the costs of this charge by saying that business-owners will have to squeeze in extra jobs to pay for it is ludicrous," said Mr Palin. "It shows that the pro-TIF campaign has a complete lack of understanding of the impact of congestion charging on small businesses.

"In addition, many small-business employers will have no choice but to pay out for the additional costs incurred by staff travelling to and from work – which will certainly not be tax-deductable expenses. Employing people is becoming increasingly difficult and a congestion charge will only add to these difficulties. Many businesses and employees are likely to move elsewhere in order to avoid paying it."

The Manchester congestion charging scheme would be the biggest in the UK. Two charging rings have been proposed; one just inside the M60 and the other around the city centre. In contrast to London, drivers would pay to cross each at peak times, when entering in the morning and leaving at night.

A referendum on the scheme is set to close at 10pm on 11 December. However, the FPB is concerned that the question on the proposed ballot papers – ‘do you agree with the Transport Innovation Fund proposals?' – is unclear and misleading because the term ‘congestion charge' is not mentioned.

FPB member Martin Cocks, of Goalcroft Ltd in Leyland, Lancashire, said he would have to pass on the costs of the charge.

"We do quite a lot of work in Manchester and, of course, we have to use the roads. If we were made to pay this charge, it would have to go on the job," he said. "In any case, the hours you work in one location are generally dictated by the environment you're working in."

Congestion charging is already a significant cost burden for many small businesses based in London, or which regularly do business in the capital.

FPB member James Taylor and Son, a bespoke shoemaker, is located on the edge of the existing congestion charging zone in London. Its Managing Director, Peter Schweiger, has experienced reduced footfall since the charge was introduced.

"As the number of cars passing by has decreased as a result of the charge, we have had a reduced number of customers, said Mr Taylor. "The number of people coming here to have their shoes specially made to measure has not gone down, but there are certainly fewer coming in to have their shoes repaired."