Ontario's auditor general says the delays and overcrowding on GO Transit are bad — and getting worse.

Jim McCarter said the transit authority must do a better job of planning for the continued increase in ridership or the situation will worsen.

In a report to the legislature on Tuesday, McCarter said up to 100,000 people ride the rails each day, but GO Transit doesn't own 70 per cent of the rail lines.

He says trains are late an average of 13 minutes are most commonly delayed by equipment failure.

But McCarter said GO Transit hasn't done any formal planning to prepare for an increase in ridership fuelled by population growth.

McCarter warns customer service will continue to deteriorate and overcrowding will get worse unless GO Transit comes up with a better plan.