Stuart Ayres will resign as NSW trade minister and deputy Liberal Leader after a draft review into the John Barilaro US job scandal found he may have breached the ministerial code of conduct.

Premier Dominic Perrottet said his resignation follows a briefing he received from the Department of Premier and Cabinet on Tuesday.

The draft report “raised a concern as to whether Mr Ayres had complied with the ministerial code of conduct”, the premier said on Wednesday.

“When I put these matters to Mr Ayres, he offered his resignation from the ministry and as deputy leader Parliamentary Liberal Party,” he said.

“An investigation will now be undertaken to determine if Mr Ayres has breached the ministerial code of conduct,” he said.

The appointment of the former NSW deputy premier and Nationals leader to a US trade job earlier this year has been an escalating scandal for the government for nearly two months.

The recruitment process is also the subject of a NSW parliamentary inquiry which resumes on Wednesday, with Investment NSW CEO Amy Brown to give evidence.