Speaking at a select committee hearing, Mr English appeared unfazed that New Zealand's Australian parent banks were getting more concerned about the prospect of a third straight year of negative profits for farmers, especially those who were highly indebted, Mr Robertson said.
"This year is set to be the most volatile in almost a decade. Bill English needs to get ahead of the game, not play catch-up.
"The Government needs to take action, not stand by on the sidelines and watch the monthly reports roll in.''
The Government needed to bring forward more infrastructure projects and take urgent action to diversify the economy away from dairy and the Auckland housing market, he said.
The Government has tagged $1 billion of spending for this year's Budget and $2.5 billion for Budget 2017, an election year.
Growing fears about China's slowing economy and heightened turbulence in financial markets was causing the Government more headaches than they did three months ago but had not spooked ministers into shifting its policy direction, Mr English told the finance and expenditure select committee.
The $2.5 billion of spending in 2017 had been partly earmarked for tax cuts but could be diverted.
"In any given time, you can construct a pretty negative scenario out of those global factors and it would be fair to say at the start of the year there was a bit more concern about the mix that's appearing than there was even three or four months ago.
"Within the fiscal track we've set, we've got some room to phase between this year and next year and we'd be a bit careful about reacting to the commentary of the week or the commentary of the month.''
Referring to the Budget, Mr English said the document would focus on delivering policies supporting more jobs, higher incomes and opportunities for New Zealanders.
An additional 175,000 jobs had been created in the past three years and the average annual wage was up by nearly $11,000 since National came into office, he said.
Budget 2016 would be about building on that success and ensuring New Zealand families continued to see the benefits of a stronger economy.
At a glance
• Budget 2016 released on May 26
• Policies to encourage job and wage growth expected in Budget
• Government's financial accounts for November due on Friday
• Call for Finance Minister Bill English to prepare the economy for shocks
