MIKE Nesbitt has said that the UUP will form an official opposition at Stormont.

Leader Mike Nesbitt said the party would not rejoin the power-sharing administration at Stormont and instead take up the recently established option of entering formal opposition to the coalition executive.

"Let battle commence," Mr Nesbitt told the Assembly chamber.

“We asked for a mandate to enter the talks on the next Programme for Government, promising that if either of our two tests were not met, we would form an Official Opposition," he said.

“Those tests were whether it was a progressive Programme and secondly, whether we sensed a will from the DUP and Sinn Féin to lead collective delivery.

“On Tuesday, it became clear the Programme for Government will not be finalised until the end of the year, seven months away. On that basis, our primary test of whether it is a progressive Programme for Government, has failed.

“Our second test was whether we sensed a will to collectively deliver the Programme and that has also failed, as it is clear the DUP and Sinn Féin will retain joint ownership of the Programme for Government."

Mike Nesbitt said that as the party felt that "little is about to change," establishing an official opposition was the "right thing to do for the country."

“The decision to go into Opposition was taken unanimously by the Ulster Unionist Assembly Group earlier today," Mike Nesbitt said.

“This heralds a new era for devolved politics at Stormont, and a big, bold step forward to normal democracy for Northern Ireland.”

We will establish an Official Opposition. We are convinced this is the right thing to do for NI. This heralds a new era for our democracy. — Ulster Unionist (@uuponline) May 12, 2016

The opportunity to create an opposition in Stormont, rather than join the executive was made possible by former MLA John McCallister's private members bill in the last term.