A leading candidate in the race to become Labour's next Holyrood leader has been accused of launching his bid to succeed Wendy Alexander before she announced her decision to quit. A key backer of Iain Gray registered a campaign website for the MSP at a time when Alexander was still in post. This is in spite of Gray insisting that he only discussed standing "in the days following her resignation".

The gaffe comes as three candidates - East Lothian MSP Gray, former health minister Andy Kerr and former justice minister Cathy Jamieson - vie to become Labour's leader in Scotland.

The trio will spend the summer locked in battle to succeed Alexander, who resigned after months of negative publicity surrounding donations to her own leadership campaign.

All candidates publicly launched their campaigns last week, but the Sunday Herald has obtained evidence that Gray had entered the race weeks before his official declaration.

A database of website registrations shows that Gordon MacRae, a PR executive who is part of Gray's circle of supporters, bought three domain names. The web addresses were purchased on June 28, the day of Alexander's resignation, but "iaingrayforscotland.org" was registered at "08:47" that morning.

This was two-and-a-half hours before Alexander read out her resignation speech at Scottish Labour HQ in Glasgow, and before she informed her shadow Cabinet colleagues of her intention to quit. It was said to have been around the time colleagues were trying to persuade Alexander to cling on as leader.

Asked at a briefing last week about how quickly he decided to stand after Alexander's resignation, Gray said: "I began to speak to colleagues in the week or so following Wendy's resignation."

A spokesman for Gray said: "Gordon MacRae is a supporter of Iain Gray, but has no official role in the campaign. He registered three domain names on the day of Wendy Alexander's resignation. He did it off his own back, without asking Iain."

But a Labour source said: "It seems a bit tasteless to register a campaign site before there is even a vacancy."

Gray, a Brownite, used the briefing to outline his views on nuclear power, the replacement of Trident and whether the parliament needs more powers.

On energy policy, Gray said he believed Scotland may need a new generation of nuclear power stations: "It seems to me nuclear is the most important low-carbon base-load production in our electricity. We will need that for some time into the future, and that could involve potentially another generation."

He said he was in favour of multi-lateral disarmament, but backed the replacement of Trident: "There is still a place for it. I'm not anti-Trident."

Gray was cautious about boosting Holyrood's financial powers, an issue being examined by the Calman Commission: "That's quite a difficult task, but I think the Commission will take it very seriously. If there is a way of doing that, then I am hopeful they will be able to suggest it."

MacRae did not return calls yesterday.

Meanwhile, the leadership contest has descended into a war of words after one of the candidates was described as wanting to take her party "back into the f***ing caves". A senior source close to Andy Kerr, the bookies' favourite, made the remark about the leadership bid of Cathy Jamieson, who is running to the left of the other candidates.

Gray and Kerr are considered to be on the modernisers' wing of the party, while Jamieson is associated with Old Labour. But the prospect of a Jamieson leadership, particularly if left-wing MSP Bill Butler wins the deputy's contest, is alarming the party's hierarchy who believe a left-wing approach would only benefit the Tories and the SNP.

A source on the Kerr campaign said: "I would rather work with Iain Gray than go back into the f****** caves with some of them. Cathy and Bill Butler, can you imagine? F*** me."

Another senior source said: "It would be a disaster if Cathy won. Her appeal is to another century. Surely to Christ, have we not moved on from that?"

Kerr used his campaign launch last week to outline his vision for the job, but it later emerged from his speaking notes that he had to have a defence of Gordon Brown prepared for him.

The script stated: "Do you support Gordon Brown ... Yes of course. He has a proven track record and I look forward to working with him."

Another part of the Kerr script focused on his recent breach of MSP rules for not declaring hospitality from McDonald's: "Mr Kerr, Wendy Alexander resigned because she had failed to register donations, you have also been found guilty of not registering gifts, why are you any different ... That was a genuine oversight on my part which I regret."

The winning candidate will be selected via a complex electoral system devised for selecting Labour leaders.

One third of the vote is reserved for party members, another third for affiliated trade unions, with the remaining 33% being allocated to Scottish MPs, MEPs and MSPs.

A spokesman for Jamieson said: "This is a charming use of language. Cathy is not running with anyone and it's for others to make up their minds and choose their language."

Part 1 - The battle for Labour's soul

Part 2 - Who will wield the dagger in the cabinet?

Part 4 - What do we in Scottish Labour need in our nation's new political landscape? A leader with guts to stand up to Westminster