The McKees said the momentum to restore devolution in the wake of the journalist’s brutal murder in April this year had waned and political parties were “failing our people”.
They expressed their fear that “more innocent people will lose their lives unnecessarily” and experience the heartache inflicted upon them since Lyra’s death.
Ms McKee was shot dead by the New IRA while observing a riot in Derry’s Creggan area.
The 29-year-old died from a single 9 mm bullet which struck her in the head.
Her family are sending postcards and letters to our 108 Assembly members, three MEPs, and 650 MPs in the House of Commons.
Letters will also be sent to Taoiseach Leo Varadkar, the Queen, and Chief Constable Simon Byrne.
The postcards have a photograph of Lyra – holding a notebook saying ‘She is the future’ – with her four-year-old great niece, Ava.
They say: “The people of Northern Ireland must have peace. Failure is not an option. Please don’t let our Lyra’s life be in vain.”
A fresh round of talks to restore devolution was announced after Ms McKee’s funeral.
The family’s letter states: “It is our hope that our appeal will remind people in a position of power and influence of the momentum to work to restore the devolved government in Northern Ireland that emerged after the murder of Lyra McKee at the hands of masked terrorists on the 18th April 2019.
“It would appear to us that this momentum quickly waned and that the political parties in Northern Ireland are failing our people.
“It is our greatest fear that this failure will lead to a return of the dark days of the Troubles and that more innocent people will lose their lives unnecessarily.
“We do not want anyone else to die and we do not want anyone else to suffer what we have been suffering since April.”
The McKees urge politicians to do whatever necessary – “even becoming courageous enough to do things differently” – to ensure that “no-one dies at the hands of terrorists in our country again”.
The family express their fear that this appeal will be ignored by the politicians.
“What is it going to take for them to get to work for the good of all of the people of Northern Ireland?” they ask.
“Are you willing to help us?
“Are you willing to help bring the much-desired peace to all of the people of Northern Ireland once and for all?
“We eagerly await your reply.”Despite five months of talks, there is no sign of progress.
An Irish Language Act remains the main stumbling block to Sinn Fein and the DUP returning to a power-sharing Executive.
Politicians from across the spectrum, including Arlene Foster, Mary Lou McDonald, Theresa May and Mr Varadkar attended Ms McKee’s funeral in St Anne’s Cathedral, Belfast.0
Five months on, no one has been charged with Lyra’s murder despite a reward offer of £10,000 put forward by independent charity Crimestoppers for information leading to the arrest and conviction of those responsible.
Lyra had been planning to get married to her partner Sara Canning before her life was cruelly ended by violent dissident republicans.