Senior minister Christopher Pyne has chastised his Coalition colleagues for publicly debating whether the government should allow first home buyers to raid their superannuation to help pay for a deposit.

Mr Pyne said those MPs seeking to "fiddle" with superannuation in the May budget risked destroying a retirement savings system that was the "envy of the world".

His intervention follows that of Prime Minister Malcolm Turnbull, who on Wednesday said the proposal had gone "round and round" and referred commentators to his 2015 comment that it was a "thoroughly bad idea".

"It's a great pity that colleagues are running these debates publicly," the Defence Industry Minister told ABC Radio.