Mixed feelings for McDonnell
Alasdair McDonnell has mixed feelings about his decision to stand down from the Assembly this summer.
The SDLP leader is to give up his seat at Stormont to focus on Westminster.
In a statement the 65-year-old MP said: "There are many conflicting emotions surrounding my decision to stand down as MLA for south Belfast.
" The people of South Belfast said they wanted me to take their cause to the floor of Parliament and I gladly accept that responsibility.
"It is now more critical than ever before that I stand shoulder to shoulder with my fellow SDLP MPs to resist the onslaught of the Tory government."
Dr McDonnell has been an MLA since 1998 and an MP since 2005. He retained his Westminster seat with 9,560 votes following the elections in May.
Last year the Northern Ireland Office passed an act banning MPs from double-jobbing.
The law comes into force when the Assembly is dissolved, expected next year for fresh elections.
He has faced criticism from high profile party members including Brid Rodgers and Seamus Mallon since saying he intended to lead the party from Westminster.
Dr McDonnell's successor in the Assembly will be selected at a party convention later this month.