The Turnbull government's $24 billion company tax cut will boost the economy by less than 0.2 per cent when fully implemented, according to a preliminary analysis by the Grattan Institute.

The federal government has been resisting pressure from Labor to outline the growth dividend from the cuts, which will see company tax fall to 25 per cent over a decade for companies with a turnover of up to $50 million, after they passed the Senate last week.

Prime Minister Malcolm Turnbull and Treasurer Scott Morrison said on Tuesday the company tax cut would deliver "substantial economic growth", but would not quantify the contribution to GDP.

Mr Morrison said while Labor argued an econometric model was needed to quantify the benefits of the cut, "I tell you what, if you go down the pub and you talk to small business people, they're not talking about econometric models. What they're talking about is how they're going to grow their businesses".