Mr Donaldson disagreed with David Trimble on key party issues
Rebel MP Jeffrey Donaldson leaves the Ulster Unionist Party after years of bitter infighting over the Good Friday Agreement and disagreements with leader David Trimble. BBC News Online charts key events which led to the Lagan Valley MP's departure.
10 April: As negotiation of the Good Friday Agreement enters its final stages, Jeffrey Donaldson walks out of the Ulster Unionist team at Stormont headed by David Trimble. Mr Donaldson expresses concern over several aspects of the agreement, including Sinn Fein holding positions in government and the early release of prisoners.
15 May: Mr Donaldson, then UUP Member of Parliament (MP) for Lagan Valley, confirms he will be voting 'No' in the forthcoming referendum on the Good Friday Agreement.
19 July: Now a prominent anti-Agreement campaigner, Mr Donaldson denies he is mounting a challenge to David Trimble's leadership of the party.
26 May: Amid intense lobbying by both anti and pro-Agreement unionists, Mr Donaldson publishes what he says is an alternative plan for devolution. He urges party delegates to demand actual decommissioning of the IRA's weapons before returning to government.
28 October: Mr Trimble wins the backing of the Ulster Unionist Council, beating off a challenge from Jeffrey Donaldson by 445 votes to 374.
23 June: David Trimble emerges from the Ulster Unionist Council's annual meeting as the unopposed leader as party opponents choose not to challenge him ahead of his scheduled resignation at the end of the month over allegations that the IRA were training Marxist rebels in Colombia.
19 September: The battle for control of the Ulster Unionist Party escalates with Mr Trimble and Mr Donaldson each attempting to persuade grass roots members to back their plans. Both men send letters to the 860-strong ruling council asking for support ahead of a crucial meeting on whether to accept government plans for an independent monitoring of paramilitary violence.
21 September: David Trimble says his party will withdraw from the power-sharing executive at Stormont on 18 January if republicans do not demonstrate they have left violence behind for good. The move follows a compromise with party hardliners at a meeting of its ruling council.
4 October: Mr Donaldson welcomes a police raid on Sinn Fein offices at Stormont, amid allegations that republicans were operating a spy ring at the Northern Ireland Office.
5 October: Mr Donaldson demands the party leader withdraws ministers from the Northern Ireland Executive, thereby collapsing the power-sharing institutions, following the Stormontgate incident and says he will call another meeting of the party's ruling council to force his leader's hand.
5 January: He says the unionist community "has lost all confidence in this process... The only way this will work is if the republican movement disbands".
25 May: Mr Donaldson threatens to leave the party if it does not reject a joint government plan designed to break the political deadlock. He says the British and Irish Governments' joint declaration breached "key unionist principles and does not provide the basis for stability in Northern Ireland".
23 June: Three UUP MPs - the Reverend Martin Smyth, Mr Donaldson and David Burnside - refuse to take direction from the party at Westminster with immediate effect, saying the leadership has failed to address party concerns. The move is designed to increase pressure on party leader Mr Trimble by refusing to endorse his policy on the British-Irish joint declaration.
27 June: The UUP suspends its three rebel MPs for their refusal to accept the party whip at Westminster. The decision leads to a summer of behind-the-scenes battles in the party over the their eventual fate.
6 September: David Trimble wins another UUC vote to back the suspension of rebel MPs Donaldson, Smyth and Burnside.
27 November: At the assembly election, Mr Donaldson tops the poll in his Lagan Valley constituency, gaining the highest personal first preference vote of the entire election.
12 December: Mr Donaldson attacks the policies of Mr Trimble and says he will work alongside the Democratic Unionist Party to bring about change.
12 December: The Ulster Unionist Party's executive approves a motion calling on Mr Donaldson to say he will resume the party's parliamentary whip and support the policies of his party.
18 December: Jeffrey Donaldson announces he has resigned from the Ulster Unionist Party, taking two other newly-elected assembly members with him - Arlene Foster and Norah Beare. Mr Donaldson says the UUP is a party that has abandoned its principles.