Four deputies have lost or resigned the party whip and another has quit the party altogether.
He quit the party on Friday, not over constitutional politics, but over Alliance's support for gay marriage.
BBC: Peter Robinson: Catholic 'majority want NI to stay in UK'
He rose to be Social Democratic prime minister in 1998-2002, but quit the party after his presidential election humiliation the following year.
Lord Rennard quit his party role in 2009 and, over the last week, he has faced accusations of sexually inappropriate behaviour towards female activists.
BBC: Lord Rennard claims: Peer reprimanded over telephone call
In August, the former Fermanagh South Tyrone MP, Ken Maginnis, quit the party after a row over controversial comments he made about homosexuality.
One of the main Sunni groups, the Iraqi Islamic Party, said on Tuesday it was quitting the government, though its representative in the cabinet, Hajem al-Hassani, told Reuters news agency that he would stay in the government and quit his party.
The Alliance Party and the Ulster Unionists both quit a cross-party working group complaining about the lack of progress.
Bob Smith of New Hampshire abruptly quit the Republican Party and announced his candidacy for president as an Independent.
Last week, the Alliance Party quit the Stormont community relations working group arguing that its recommendations on issues such as flags were not strong enough.
Relations between Ms Andreasen and Mr Farage had been strained for some time, with Ms Andreasen calling for Mr Farage to quit after the party's poor performance in council elections in 2011.
Mr Netanyahu, who was appointed caretaker foreign minister last week after the Labour Party quit the coalition government, has repeated his call for the forcible deportation of Mr Arafat from the West Bank.
Both men have quit the Ulster Unionist Party over the decision of the party to support a unionist unity candidate in the Mid-Ulster by-election.
She quit the paternal United Party in 1959, frustrated that it was so wobbly against apartheid, to join a Progressive Party of 12 members that was wiped out in an election two years later.
Attlee was unable to subdue Nye Bevan - a heroic figure for the party's left - who quit the shadow cabinet and was almost expelled from the party a year later.
Mr Allawi is a secular-minded member of Iraq's Shia Muslim majority, who quit Saddam's Baath party in the 1970s and, with the backing of American and British intelligence, formed the Iraqi National Accord, which opposed Saddam from exile.
He told Minnesota party members in a letter outlining the reasons for his decision to quit that the potential for a third major national party still existed.
One of al-Watan's founders, Emad Abdel Ghaffour, was Nour Party leader until he quit last week following internal disputes over the role of clerics in decision-making and bickering over internal elections.
His implicit threat to quit came at a meeting of party workers as he embarked on a campaign to win support for his plans ahead of a party conference on June 1st.
Another, Andrew Percy, reportedly claimed party members were threatening to quit because of Mr Mitchell's behaviour.
In 1990, the former Tanzanian President Julius Nyerere bowed out of mainstream politics when he quit as chairman of the ruling CCM party.
The chairman of Bristol UKIP has quit and will not be standing for the party in May's local elections following comments on illegal immigrants.
BBC: UKIP Bristol chairman quits 'after immigration comment'
Mr Trimble pledged to his party last year that he would quit if the IRA had not started decommissioning its arsenal by the end of January, saying that there cannot be an "armed peace".
To seal the strained relations between the two former political buddies, Mr Mutharika quit the UDF and founded his own Democratic Progressive Party.
Mr Berlusconi quit as prime minister after Mr Fini's party, the National Alliance, threatened to follow the Christian Democrats by pulling out of government.
Before long he was openly jockeying for the leadership and was the media face of the party for its 2004 European election success - but when Mr Knapman refused to stand aside for him, Mr Kilroy-Silk quit and formed his own short-lived rival party.
Original leader and UKIP founder Alan Sked quit before the 1999 European elections, after arguing the party should refuse seats in the "gravy train" of the Strasbourg Parliament.
The Tea Party drove one long-time Republican operative to quit after 30 years as a Capitol Hill staffer.
David Miliband quit the shadow cabinet after losing the close vote for the party leadership, in which he was clear favourite and lost out because Ed secured trade union votes.
President Abdurrahman Wahid has demanded that the central bank chief should quit because of his role in the financial scandal involving the Golkar party of former President Suharto.
An ex-Royal Navy medical officer is to stand for the National Health Action Party in the Eastleigh by-election after disgraced Chris Huhne quit.
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