The scheme is intended to go to the south and east of the city
A £400m tram extension in Nottingham could be scrapped if the Conservatives take control of the county after next month's county council elections.
The Conservatives have been campaigning in Beeston and said bus services should be improved instead of putting cash into the trams system.
Labour has accused the Conservatives of being short sighted over the scheme.
The Liberal Democrats said they would support the tram scheme extension and said millions of pounds had been spent.
Conservative spokeswoman for Work and Pensions and shadow Minister for Women Teresa May was campaigning in Beeston where she said the Tories considered the scheme too expensive.
Mr Kirkham said trams were a cleaner form of transport than buses and cars
Ms May said: "What we're saying is very simply, it's an awful lot of money, nearly £30m for this extension of the tram which would have to be paid for across the whole of the county."
The scheme would link Clifton in the south and go out to the west.
But the Labour leader of Nottinghamshire County Council, David Kirkham, said the tram scheme was the best option for future transport needs.
He said: "We see the tram as the future of public transport in Nottinghamshire.
"It's a much cleaner, environmentally friendly form of public transport than buses and cars and we've got to do something about the congestion in Nottingham and those parts of Nottinghamshire."
The leader of the Liberal Democrats on the council Stan Heptinstall said: "I'm absolutely horrified.
"All this money that's been spent on the tram, bringing it up to this point in time and then for it simply to be thrown away, simply to get votes for an election is absolutely appalling.
"The tram should go forward now, millions of pounds have been spent.
"It would be a huge, huge mistake to stop the progress of it now."
The cost of travelling by tram in Nottingham has increased, with some fares going up by 30%.
While some tickets have remained the same, particularly child prices, the cost of 10 single journeys has jumped from £10 to £13.
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