Sydney University has warned of the "serious impact" on thousands of students, staff and other commuters of a decision for trains on the Blue Mountain Line to no longer stop at Redfern station, making their trips "lengthier and more challenging".

In a swipe at the state's transport agency, vice-chancellor Michael Spence said the decision for trains on the line to bypass Redfern in favour of Central Station had "added greatly to the university's already significant public transport pressures".

"We are disturbed that we were not consulted about such a significant change," he said in a letter to the state opposition.

Dr Spence said Transport Minister Andrew Constance had identified demand for trains "going through the roof", and "yet he had allowed a timetabling change which makes train travel for thousands of our students and staff lengthier and more challenging".