Finance Minister Mathias Cormann has played down criticism of his handling of the budget by a disgruntled government backbencher.

Western Australian David Jensen, who lost Liberal pre-selection for the next election, took to Twitter for a second day to voice his concerns about this week’s federal budget.

“If Corman(n) was more focussed on his job as finance minister, and less as powerbroker arranging pre-selection, would be less deficit,” he tweeted on Thursday.

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Mr Cormann was happy to tell a Senate committee and Dr Jensen that he had been totally focused on putting the budget together.

“Let me assure you that everyone in the Turnbull government has been fully focused on our plan for jobs and growth,” Mr Cormann said.

But the minister was cagier about the full cost of the government’s 10-year enterprise tax plan, outside the $2.7 billion costed over the four-year budget estimates.

“After a projected return to surplus 2020/21 the budget is projected to remain in surplus over the medium term which clearly indicates to you that the cost of this 10-year company tax plan … is fully costed and fully funded,” Mr Cormann said.

The budget was handed down on Tuesday, a week earlier than previously scheduled as part of the process for a double-dissolution election on July 2.

The Department of Finance took it upon itself to game-plan an early budget, even before Prime Minister Malcolm Turnbull confirmed the change in mid-March.

“There was speculation, so we thought about it in case, but we didn’t change any of the timetable until there was a decision,” department secretary Jane Halton told the hearing.

– AAP