Former Liberal leader John Hewson says the aim of both major political parties to return the budget to surplus at all costs is nonsensical.

Labor and the coalition persistently talk about returning the budget to surplus - in the government's case it is predicting a return to balance in 2015/16 and a surplus in 2016/17.

"This blinded objective of achieving a budget surplus at all cost, as fast as possible, is nonsensical (from) both sides of politics, particularly in circumstances when the economy is flattening out," Dr Hewson told the National Press Club on Wednesday.

He also believes it is a weakness that neither side of politics is prepared to express views about interest rates.

"You have handed over authority and independence to the Reserve Bank, but you are not prepared to state a position," Dr Hewson said.

"You don't see that in other countries, there is a pretty wide expression of opinion and debate about such things."

He believes the cash rate should be 1.5 per cent rather than its current rate of 2.75 per cent.

He also thinks Opposition Leader Tony Abbott's version of a generous paid parental scheme is a good idea despite its cost.

Mr Abbott, who used to work for Dr Hewson when he was Liberal leader, says his plan will be funded by putting a levy on big business.