Mr McConnell said: “Members of the Scottish Parliament and the party members in Scotland make a choice without any influence either from me, as someone who has been in the position in the past, or from senior figures in the party leadership elsewhere.

“We need to have the candidates set out their stall, give them a chance to show the leadership qualities they think they have but also have a real debate about Scottish Labour and how we put our values and principles into practice for the 21st century. A coronation would be the wrong thing to happen for a whole number of reasons.”

His comments were backed by predecessor Henry McLeish, who called for a free vote and said it should happen as soon as possible.

Mr McLeish said: “We do need a contest, there is no obvious favourite to replace Wendy and that is why I think within Holyrood and within the party structure in Scotland, we should have a vote.”

Any Labour MSP can stand but candidates have to have the support of one eighth of the parliamentary Labour Party.
With 46 Labour MSPs, this makes the threshold six – a contender plus at least five MSP backers.

If only one nominee comes forward the party’s Scottish executive and Labour MSPs confirm the nominee as the new leader.

Meanwhile, there was more woe for Mr Brown when a Labour donor declared him “an incapable leader”. Prime wealthy donors who bankrolled Labour under Tony Blair broke ranks to reveal they may not support his struggling successor.

Business guru Sir Gerry Robinson, who has given Labour £70,000 since 2001, signalled he would probably give no more while Mr Brown was leader.

The former Granada TV chairman added: “Labour look in a lot of trouble and Brown is showing all the signs of not being a capable leader. These crises don’t happen accidentally. It’s not just an issue of timing.

It’s an issue of getting it right or not getting it right. And it doesn’t feel right. It’s probably an impossible position to come back from.”

Criticism also came from millionaire electronics tycoon Sir Maurice Hatter, who has given more than £176,000 to Labour since 2001. He said it was time to replace Mr Brown.

He added: “He hasn’t got the charisma. He was a good No.2 but he is not a No.1. The party would be better without him.’’

Author and businessman Sir Christopher Ondaatje who has donated £1.6million, said the “dangerous decision” to bail out Northern Rock with public funds would end in disaster, while Everton football club chairman and theatre producer Bill Kenwright, who has given £255,000, said Labour had “lost touch with the people’’.

Lord Levy, Labour’s chief fundraiser under Mr Blair, said it seemed “very difficult’’ now to get large donations in. He added: “The party needs to consider the leadership.”