Lib Dems in disarray as leader Stephen quits

He told parliamentary colleagues he could not juggle the demands of the job with his family life. The MSP has four children and it is understood he has found it increasingly difficult to spend time with his family in Aberdeenshire while being party leader. He will remain as an MSP for Aberdeen South.

His resignation means there are now two parties looking for a leader after Wendy Alexander's decision to step down as Labour leader last week amid a row over leadership campaign donations.

"It has been an honour to lead the party over the last three years," Mr Stephen said last night. "Everyone involved in politics knows that there are stresses and strains on family life. The health and wellbeing of your family has got to come first."

And he added: "Perhaps my announcement today should alert people to the demands placed on politicians and their families."

He is married to Caris and they have two sons and two daughters aged between four and 12.

Mr Stephen's decision to stand down will spark a leadership contest with Tavish Scott, the MSP for Shetland, the clear favourite to replace him.

Mike Rumbles, the independence-minded MSP who stood against Mr Stephen in the battle to succeed Jim – now Lord – Wallace, last night confirmed he would run, adding:

"I am heartened by the numbers of people contacting me and asking me to stand. Having stood before I am ready to do it again. I feel I have a lot to offer the party."

The leadership election process is likely to conclude by early September. Michael Moore MP, the deputy leader, will take the role of acting leader.

Mr Stephen had a poor election last May when his party came fourth behind the Tories. The Lib Dems had served in coalition rule with Labour for eight years.

Mr Stephen stayed on to lead his party in opposition but refused to enter a coalition with the SNP because of Alex Salmond's insistence on a referendum on independence. He surprised many with the way he has scored points at First Minister's Questions, consistently getting the better of Mr Salmond.

Lord Wallace said: "Nicol Stephen can move on, confident his achievements in government and opposition will stand the test of time."

Audrey Findlay CBE, national convener of the Scottish Lib Dems sent an e-mail to party members. It read: "Family life is important to everyone. You cannot re-run a child's childhood."

Annabel Goldie, the Scottish Tory leader, said: "Families are paramount. We wish Nicol and his family the best for the future."

Nick Clegg, the Liberal Democrats' leader, said Mr Stephen was an "outstanding politician and force for change in Scotland", adding: "He will remain an important figure in the Liberal Democrats."

IN QUOTES

"Everyone involved in politics knows there are stresses and strains on family life. But when you have to make a choice between family and politics the health of your family has to come first."

"With four children between the ages of four and 12, my family has to be my priority."

"I have been away from home at least four working days each week for more than nine years."

"As party leader, the responsibilities have been even more demanding. There is rarely a weekend, birthday or family holiday when the demands of the job do not intrude. It can have an impact. And when that impact becomes too great, it is time to put my family first."

"My hunger for change in Scotland is no less now than when I started in politics 25 years ago. However, that drive and that passion comes at a price. And it is a sacrifice that my family should no longer have to make. Their happinessis more important than any political office and that is the reason for me standing down."