Following meetings with property owners on George Street and developers, Sydney lord mayor Clover Moore said it had become clear that "adequate results" had not been reached in a number of critical areas across the entire 12-kilometre route.

"What we are expecting is a sensitive urban project, not a heavy rail, suburban railway through the heart of a global city [along George Street]," she told Fairfax Media.

"It is not just about cutting a ribbon for the next state election. We just want what we thought we were getting."

The council's main beef is that shelters proposed for George Street, outside the Queen Victoria Building and Wynyard, are too large and imposing, while not enough trees will be planted to create an "effective boulevard" along the pedestrian parts of the popular thoroughfare.

Cr Moore said the existing awnings on buildings would provide enough cover from bad weather for passengers waiting for trams.

She has penned a letter to Premier Mike Baird calling for a "responsive and sensitive approach for these two high-profile, pedestrianised and sensitive heritage precincts" on George Street.

The council has committed $220 million towards the $2.1 billion cost of the light rail line, which will run from Circular Quay to Randwick and Kensington in Sydney's south east.

While it has already handed over $68 million, it is now threatening to withhold the next payment of $47 million due in December unless contractual obligations are met.

"The City has already had significant discussion with the project team and contractors and your direct intervention is now needed to address the blockages and ensure a way forward," Cr Moore wrote in her letter to the Premier.

"The City has written to the independent certifier detailing areas where fundamental obligations in our project agreement are not being met."

Paspaley Global Retail general manager Richard Broug said the planned shelters were "far too big and not necessary", and ran contrary to the original plans by the project team.

Likewise, the trams would be too long and not enough trees were planned for George Street, he said.

"What I am concerned about is that politics are getting in the way of achieving a best outcome for the city," he said. "We have a once-in-a-generation opportunity to get this light rail line right."

The company owns 2 Martin Place, the former Bank of Australasia building.

The 67-metre trams that the government plans to run along the line will make them among the longest in the world, second only to those in Marrakesh in Morocco.

Cr Moore said the council wanted the government to look at making the tram sets shorter – especially those running during off-peak periods – to ensure they did not dominate George Street.

"We didn't know they were going to sign a contract for a tram that is 67 metres long," she said.

A spokesman for Mr Baird said the Lord Mayor's correspondence "will be responded to in the usual way".

Cr Moore has sought to meet the Premier as early as this Thursday to address the concerns before the government signs off on the final designs for the light rail line.

Completion of construction of the line along George Street has been already been delayed by up to five months, after about 400 unused cables were discovered under the roadway.

The government had originally wanted work on two zones in George Street finished before Christmas to avoid disrupting the busiest shopping period of the year.