Arlene Foster said she took great pride in the fact she was the first woman to hold the post when this afternoon in the Northern Assembly she was formally elected as Northern Ireland's First Minister.

Ms Foster also told Assembly colleagues that she saw it not only as her legal duty but a "moral imperative" to serve everyone in Northern Ireland.

When Peter Robinson stood down as First Minister this afternoon under the rules of the Assembly a new First Minister and Deputy First Minister had to be returned.

Ms Foster was formally elected as First Minister and Martin McGuinness was returned as Deputy First Minister after they both affirmed the pledge of office to work the powersharing institutions including the North-South bodies.

Ms Foster said she was tired of Stormont “being a watchword for arguing and bickering” and pledged to do all in her power to “change the political culture of this place”. She said she wanted accommodation with one another rather than conflict.

Ms Foster (45) well as taking pride in being the first woman to hold the post said she was also proud that she was the youngest women in the 95-year history of Northern Ireland to hold such a post.

She said she was humbled by her appointment. She paid tribute to members of the British army and police who died in the Troubles and more generally remembered those who suffered as a result of the violence.

She also honoured the memory of her late father who as an RUC officer and when she was young was wounded in an IRA attack.

While remembering the past she added: “We can’t allow the past to forever blight our future.”

Mr McGuinness in congratulating Ms Foster acknowledged the “hurt” her family had “endured as a result of the conflict”. He also referred to the hurt and losses suffered by people from the republican community.

Mr McGuinness expressed confidence that he and Ms Foster would work well together in a constructive and positive leadership and with a “good heart”.

Mr Robinson in standing down said the combined unionist-nationalist political rejection of dissident violence demonstrated that Northern Ireland would never go back to the dark days of the past.

Mr Robinson in his short valedictory in the Assembly chamber this afternoon paid tribute to the Sinn Fein Deputy First Minister Martin McGuinness and recalled how both of them stood shoulder to shoulder after dissident republican killings such as those of British soldiers Patrick Azimkar and Mark Quinsey, PSNI officer Ronan Kerr and prison officer David Black.

“Strangely we were at our strongest when the threat from outside to the institutions was at its greatest,” he said. This, he added, was the “surest sign” that Northern Ireland was “never going back to the dark days of the past”.

Mr Robinson said Stormont had had its “share of trials and ordeals but through them all we have emerged much stronger”.

He said that from his long years of service he had learned that there were “very few” politicians who were not motivated to act in the best interests of society. “I admire people who devote their lives to public service,” he said.

Mr Robinson said that some people would be disappointed with the current pace of political change, some would say it was happening too fast, some too slow but nonetheless “so much has been achieved”.

He said that “devolution underpins the level of peace and stability” that Northern Ireland enjoyed today.

Mr Robinson said he would not interfere in the work of Arlene Foster as DUP leader and First Minister but would always be there to offer advice and support if requested. In finally standing down as First Minister he expressed confidence that the powersharing institutions “will be here for generations to come”.

Ms Foster before she was formally elected as First Minister said she had “enormous shoes to fill” in succeeding Mr Robinson. She said he had ensured the survival of the Northern Executive and Assembly through “rocky” periods.

Mr McGuinness expressed his “deep appreciation” to Mr Robinson. He said when he first began working with him when he was appointed First Minister in 2008 that Mr Robinson said to him that “no matter what happens on the streets we must ensure that these institutions don’t collapse”.

He said they had faced many “huge challenges” but had come through with the institutions intact.

Mr McGuinness said he had enjoyed a friendship with Mr Robinson’s predecessor Ian Paisley and was sure his friendship with Mr Robinson would also last a lifetime.

Taoiseach Enda Kenny congratulated Ms Foster on her election and wished her every success at “an important time for Northern Ireland”. He looked forward to “continuing to work with her to meet challenges and develop opportunities”.