A decision on whether to back the £425m Circuit of Wales with public money will not be taken until about mid-May.
Economy Secretary Ken Skates said the firm that wants to build the motor racing track near Ebbw Vale had still not provided all information required.
He also claimed developers had not provided paperwork needed to start the due diligence process until last week.
The Heads of the Valleys Development Company (HOVDC) said it had "taken time to compile all information requested".
Mr Skates said on 8 February he would look in detail at the latest financial plans for the project, saying the process would take four to six weeks.
But on Wednesday he told AMs the documents needed to complete the due diligence arrived late last week and that it was "regrettable that the information is currently incomplete".
He said he hoped to report back to the cabinet by mid-May - after the council elections on 4 May.
The track would be built with private funding and would host Moto GP races.
Mr Skates told the Senedd on Wednesday claims that the track could create up to 6,000 jobs in one of Wales' most deprived communities will be "thoroughly scrutinised" by consultants who are carrying out the due diligence on behalf of the Welsh Government.
A "fit-and-proper persons" test started this week into directors of HOVDC.
"We will not bypass due diligence for any decision," Mr Skates said.
"We have been applying immense pressure to the developers to provide the information that is required of them by the consultants. With that information due diligence can be completed."
It was in the company's interest to comply "so the people of Ebbw Vale and the valleys know whether this is a viable project", he added.
Responding to the delay, Plaid Cymru economy spokesman Adam Price said: "If there has been a problem with a lack of complete information why hasn't the government done what the private sector would do in these kinds of situations, in projects which are far larger than this, which is to get everyone in a room... so that we can actually sort this out?"
Auditor General Huw Vaughan Thomas is separately investigating more than £9m that the Welsh Government has already provided to the scheme.
His report is expected some time in April.
A Circuit of Wales spokesman said HOVDC welcomed the start of the due diligence process by the Welsh Government.
"Given the seven years of activity, it has taken time to compile all information requested by them and their advisors," he said.
"We acknowledge the significant efforts by the officials and our respective teams to ensure that our project meets the challenging metrics set out last year and will continue to work with enthusiasm, dedication and effort to deliver this transforming project for Wales.
"We also continue to be available to meet with Welsh Government officials and its advisors and stand ready to do all we can to accelerate any of their work to allow a decision to be made as early as possible."