THE number of bus journeys in Adelaide may fall by 2.2 million as commuters deluge the Government with complaints about transport services every day.

There were 65.95 million journeys on Adelaide buses in financial year 2010-11, but this year's result is is estimated to be 63.7 million - well short of the target of 70 million.

In Budget Estimates hearings yesterday, Transport Services Minister Chloe Fox said the Government was being inundated with calls, despite listing the troubled bus contracts as a highlight of 2011-12.

Ms Fox said the Government was doing all that it could to resolve the transport problems by implementing multiple strategies but it was now up to the contractors to "do their bit".

"We are trying our very best," Ms Fox said.

"We are introducing the new timetables, we are introducing the new bus priority lanes, we are introducing the GPS. All of those things should help us work with contractors to get the result that South Australians deserve.

"It is now up to the contractors to do their bit."

Opposition spokeswoman Vickie Chapman said that increased spending had resulted in failure.

"The number of people catching the bus has gone down significantly in the past year and Minister Fox has set the target for next year lower than last year," Ms Chapman said.

The estimated total bus boardings for 2012-13 is now 65.3 million, a drop of 4.7 million from this year's target.

"The Government has thrown more money and a second minister at the bus problems and the result has been a failure. Following yesterday's Budget Estimates hearing, Ms Chapman went as far as to call for Ms Fox to be sacked.

"Ms Fox is floundering and bus commuters are feeling the pain as a result," Ms Chapman said.

"Today was the clearest example yet that she does not have what it takes to be a minister of the Crown.

"Premier Weatherill must act and save the $1.5 million per year Minister Fox and her personal staff receive."

Ms Fox said last night: "This is predictable sledging from the Liberals; a party that continues to offer no solutions, no original ideas and no vision for South Australians."