In a statement here, former minister and SAD general secretary Bikram Majithia said Sidhu should explain why he ordered "sub-standard" fire tenders to an inquiry commission.
The Akali leader said it must be ascertained whether the fire tenders were newly manufactured or simply refurbished and repainted vehicles.
Eleven fire fighting vehicles were yesterday flagged off here by Sidhu, who is the local bodies minister.
Majithia said the issue was important because Sidhu had ordered eight more fire tenders whose delivery is expected next week.