Talks to restore Stormont powersharing should begin immediately following Lyra McKee's murder, SDLP leader Colum Eastwood has said.
Mr Eastwood wrote to Taoiseach Leo Varadkar and British Prime Minister Theresa May following the death of the promising young journalist in his native Derry on Thursday.
He said a clear message had been sent to the gunmen from communities in the Creggan estate where the tragedy occurred, and across Ireland.
"There is an unmistakable public desire that the tragic and terrible loss of Lyra McKee marks a turning point for our peace and political process.
"I am therefore writing to all party leaders and to the two governments to urge that talks are convened this week in order to finally restore government in Northern Ireland.
"On the streets of Creggan, in Derry and across Ireland a clear and resolute message has been sent to Lyra's killers and to all of those still wedded to the futility of violence.
"They are the enemies of all of us on this island and enemies of the shared future we have all chosen to build."
DUP leader Arlene Foster and Sinn Féin leader Mary Lou McDonald together attended a vigil on the streets of the Creggan in the hours after the killing.
They have not held political talks for months amid deep differences surrounding issues like the place of the Irish language.
Sinn Féin is opposed to returning to devolved government until disputes such as that over the ban on same-sex marriage in Northern Ireland are addressed.
Mr Eastwood said the aftermath of the murder gave a simple and direct message to political leaders to resolve their differences and get back to work.
It is 21 years since the Good Friday Agreement but the Foyle Assembly member said people had become far too casual about the risk posed by political vacuum.
"We have too easily forgotten that failure in our politics always results in danger in our streets.
"We have been far too ready to disagree with one another and not ready enough to value and build upon the peace we inherited.
"As political leaders, we are responsible for the context of political division which has let all of our people down. We can't allow it to go on."
He said that reform of the petition of concern which allows a veto on contentious legislation was central to unlocking the impasse and claimed there was a lack of political courage and will to do a deal.
Local government and European elections are due in Northern Ireland next month and Mr Eastwood is to run for the European Parliament.
Traditionally, the period before polls open is an unpromising one for deal-making but the SDLP leader said that excuse should be removed.
"The public expect us to go back to work and they expect us to form a government, campaigning for any election can't get in the way of that fundamental responsibility.
"We have to stop failing and we need to start talking."