A fast train link could reduce the travel time between Parramatta and the Sydney CBD to 15 minutes, according to a new report spruiking better connectivity between the two centres.

The report, commissioned by Parramatta Council and the Sydney Business Chamber's western Sydney branch, presents four route options in broad terms but does not define the costs of the lines or who would pay for them.

It also proposes a connecting rail link between Parramatta and the future airport at Badgerys Creek via either Blacktown or Liverpool, with a travel time of 25 minutes.

The first option for fast rail between Parramatta and Sydney CBD with stops at Lidcombe and Strathfield would require the conversion of the existing Western Line, but the report dismisses this as expensive, disruptive and incapable of significantly reducing travel time.