Melbourne’s trams have recorded the worst cancellation rate in almost two decades.

Data prepared by Public Transport Victoria (PTV) shows more trams were cancelled in January than in all of 2010.

In the first month of 2019 Yarra Trams cancelled a total of 4196 services, which is more than the annual cancellations in 2006, 2008, 2009 and 2010, and the worst figure on publicly available records; which date back to 2001.

PTV's boss admitted that parts of the city's ageing system can't cope with warm weather. (9news)

It’s prompted an admission from PTV boss Jeroen Weimar that parts of the city’s ageing system can’t cope with warm weather.

“We made the decision in January that on the hot weather days we would actually take some of the older trams off the road, because we know they break down in hot weather,” Mr Weimar said.

On route 82,579 trams were cancelled, while a further 536 were cancelled on route 30.

PTV's boss admitted that parts of the city's ageing system can't cope with warm weather. (9news)

Other badly affected lines were routes 78, 19 and 6, with 448, 328 and 311 cancellations respectively.

Many of those services were replaced by buses, but Public Transport Users Association spokesman Daniel Bowen argued that’s not a long term solution.

“You can't say our tram system is partly going to run as buses forever more,” Mr Bowen said.

“The government needs to invest in more air-conditioned trams and get those older trams in the fleet replaced with newer ones.”

A total of 579 trams were cancelled on route 82. (9news)

Some of the city’s trams were delivered in the late 1970s.

PTV said the cancellation of selected services allowed Yarra Trams to improve reliability on more heavily used parts of the network.

Public Transport Minister Melissa Horne declined to comment, but her office issued a statement highlighting the government’s investment in 90 new E-class trams; 74 of which are currently on the network.

“The former Liberal Government didn't order a single new tram in four years,” it said.

“Our new contract with Yarra Trams sets higher performance targets to make sure more trams arrive on time and cancellations are reduced.”

But Shadow Transport Minister David Davis poured scorn on that claim.

“They say that they've got new contracts, but the new contracts are clearly not working,” Mr Davis said.

“The system is getting worse”.