SDLP deputy leader Dr Alasdair McDonnell will this week announce he is standing for the party leadership.


McDonnell will be running against the North's social development minister, Margaret Ritchie, in what will be an extremely close race. The new SDLP leader will be elected at the party's annual conference in February.


McDonnell said the election presented a "tremendous opportunity to refocus, reinvigorate, re-energise and rebuild the SDLP". Once the North's largest nationalist party, the SDLP has been completely over-taken by Sinn Féin in the last decade.


Mark Durkan last month announced he was standing down as leader. McDonnell said the SDLP had worked tirelessly for peace but there was still much to do: "That will require a leader determined to build on the wealth of experience and wisdom in the party, while bringing in new and talented young women and men.


"A team player committed to the challenge of change who will put passion, confidence and ambition back into our party. The days of the SDLP being sidelined are over. It's time for us to reassert ourselves."


McDonnell (60), the South Belfast MP, will formally announce his candidature on Tuesday. At 5/4, Margaret Ritchie is the bookies' favourite with McDonnell close second favourite at 6/4. He is supported by several Assembly members, including Patsy McGlone from Mid-Ulster.


Ritchie is supported by Alex Attwood from West Belfast, Carmel Hanna from McDonnell's own South Belfast constituency, and Dolores Kelly in Upper Bann. Attwood described Ritchie as the most popular politician in the North.


Ritchie's attempts to stop funding for a UDA-linked project won widespread admiration and she is one of Stormont's most high-profile ministers. However, McDonnell's supporters say he possesses the gravitas and political nous to challenge Sinn Féin and reverse his party's electoral fortunes.


The votes of delegates from South Belfast, South Down, and Foyle – the largest SDLP constituencies – will be pivotal.


McDonnell's candidature will be announced in Belfast's Old Museum Arts' Centre – next door to the SDLP's original headquarters – in line with his theme of rebuilding the party.