The levy would start at £250 per car annually in 2012
Conservative Party leader David Cameron has supported a House of Commons motion calling for Nottingham's workplace parking levy to be scrapped.
The motion was signed by shadow transport secretary Patricia Villers and several other MPs.
The party had earlier said it would "take a second look" at the parking levy.
City council leader Jon Collins said any move to scrap the levy would effect plans for a tram extension.
Mr Collins said: "If it is Conservative policy not to support the levy and therefore not to support the tram they should come clean and not try to slip it out under a minor parliamentary procedure.
"No workplace levy, no tram," he said
The workplace parking levy would initially cost motorists £250 per space annually, raising £14m a year.
Any move to scrap the levy would be time-consuming and costly, Mr Collins said.
The Early Day motion was presented to the House of Commons by Ms Villers and signed by Cameron.
The Tories have indicated they would oppose the levy because it would mean job losses.
The money raised in the levy would also be used to refurbish the city's train station and the widening of the congested A453.
The proposed parking levy has already been delayed once - until 2012 - due to the recession.
Business leaders have also expressed concerns the levy could force some some firms to move outside the city.