Tasmanian Governor Peter Underwood did not believe the Liberals could form a stable government when he decided on Thursday that Labor should retain government following the March 20 election’s split result.

Mr Underwood on Thursday invited Premier David Bartlett to test his numbers in the state’s lower house, after the poll delivered 10 seats to both Labor and the Liberals, and five to the Greens.

The decision was a surprise.

Mr Bartlett on Wednesday had advised the governor to accept his election campaign promise that he would resign as premier in the event of a tie if the Liberals emerged with the greatest overall vote.

On Thursday, the Tasmanian Greens decided to back a minority Labor government.

The governor on Friday released his reasons for allowing Mr Bartlett the chance to secure the confidence of the lower house.

“I came to the conclusion that (Liberal leader Will) Hodgman was not in a position to form a stable government,” Mr Underwood said in a statement.

“Consequently, I was obliged to send for Mr Bartlett.

“I … told him that as he was still the holder of my commission to form a government and the premier of the state, he had a constitutional obligation to form a government.”

Mr Hodgman said Mr Bartlett had recanted on a promise to allow him the first opportunity to try to form government and had doctored a document he gave to Mr Underwood detailing a pledge not to move a no-confidence motion against any Liberal minority government.

“From what I understand, Mr Bartlett or his office has provided an incomplete transcript which excludes that most important and significant commitment that in my view should have been provided to His Excellency,” Mr Hodgman told reporters in Hobart on Friday.

Mr Bartlett maintains he never made that promise, saying he had only given the promise to advise Mr Underwood to allow Mr Hodgman the first chance to form government because the Liberal Party secured more primary votes.

“I kept my commitment to the Tasmanian people that in the event of a 10-10 result, with the Liberals receiving more of the overall popular vote, I would give the Liberals, via my advice to His Excellency, the first opportunity to form government,” Mr Bartlett said.

But Mr Underwood said it was not for Mr Bartlett to decide who should govern.

“The commissioning of a person to form a government is entirely the governor’s prerogative and it is not within the gift of any political leader to hand over,” Mr Underwood said.

“The total number of votes received by the elected members of a political party is constitutionally irrelevant.”

Mr Bartlett on Friday also denied doing a deal with the Greens, saying he hadn’t had talks with the party since “well before” election night.

“It was as much a shock to me yesterday as it was to anyone that (Greens leader) Nick McKim made that move,” he told ABC Radio.