Report on minister's conduct received by Carwyn Jones
A report on Environment Minister Alun Davies's conduct has been received by First Minister Carwyn Jones who will respond "in due course", his spokeswoman said.
Permanent Secretary Sir Derek Jones had been asked to investigate whether Mr Davies broke the ministerial code.
Mr Davies wrote to the environment watchdog over plans for a race track near Ebbw Vale, in his constituency.
The review looked at whether there was a conflict with his ministerial role.
His post includes oversight of Natural Resources Wales (NRW).
The body initially objected to the £280m Circuit of Wales scheme but later said its concerns had been addressed.
It is understood Mr Jones received the report on Wednesday, on his return from a Nato event in Brussels.
A Welsh government spokeswoman said: "The first minister has received the permanent secretary's review and will make a statement in due course."
Conservative AM Antoniette Sandbach said: "These are extremely serious concerns and answers are now overdue.
"The ministerial code is very clear and the minister's actions are extremely disturbing.
"If a Labour minister has used his position to secure an advantage in his own constituency - strong action must be taken by the first minister.
"Given the millions in public money that is tied up within the Circuit of Wales project, the results of this investigation should be published urgently."