Nosiviwe Mapisa-Nqakula won't say how much her department has budgeted for the new aircraft.

CAPE TOWN - Defence Minister Nosiviwe Mapisa-Nqakula says her department is going ahead with procuring a new presidential jet, but she is refusing to say how much the government is willing to spend.

She was speaking ahead of her department's budget vote presentation in Parliament today.

Based on the specifications for the new aircraft published by Armscor, the defence force's acquisition's agency, last year an unofficial estimate put the cost at R4 billion.

Armscor went ahead and published details of the tender for the new presidential jet last month.

But Mapisa-Nqakula won't say how much her department has budgeted for the new aircraft.

"We're adults and as adults, we are responsible; a government which is sensitive; we would never ever sit here and say we will spend R4 billion on an aircraft. Obviously work has to be done, which will determine depending of course, on the responses which we receive."

Due to delays in finalising the purchase of the new jet, the defence force will, in the meantime, make use of leased aircraft.

"There was very little movement obviously because there are certain things we have to consider from the feedback, which we had received from the companies. So we could not meet our own deadline, which we had set for ourselves which was 31 March. What are the implications of that? The implications of that are that one, we are now preparing to lease an aircraft and we are going to lease an aircraft whilst we are in the process of procuring one for the VVIPs… because one thing we are not going to do is to compromise the security and the safety of our principles."

Opposition parties have slammed the decision to buy a new jet, saying it's unaffordable.