Prime Minister Malcolm Turnbull has cooled expectations of an affordable housing "centrepiece" in the budget, even as junior minister Michael Sukkar promised a policy to help first home buyers save a deposit without raiding superannuation.

For months, senior government sources have privately briefed that the housing affordability package would be the centrepiece of the budget – though they have carefully avoided saying this in public.

But in a clear sign the government is still grappling with rapidly diminishing policy options before the May 9 budget, Mr Turnbull tamped down expectations that housing affordability would be at the heart of the budget.

"I've read that in the press, but I don't think that's a fair description," he said on Friday. "The focus of the budget is, and has to be, firstly driving continued strong economic growth. That is the tide that we have to ensure lifts all boats."