Election watchdogs will not issue their findings on the illegal donation made to Wendy Alexander's leadership campaign until the New Year, it emerged yesterday.

Ms Alexander handed over details of all contributions made to her campaign to the Electoral Commission a fortnight ago and it had been hoped that a decision on what course of action to take would be made by Christmas.

But an Electoral Commission source yesterday revealed that it planned to make no comment on the matter until next year.

Ms Alexander's campaign team have already admitted it broke the law by accepting a £950 donation from Paul Green, the multimillionaire retail tycoon who lives in Jersey and is therefore ineligible to vote in the UK and banned from making political donations under the Elections Act.

The donation was solicited by Glasgow Cathcart MSP Charlie Gordon, who has also admitted accepting £950 from Mr Green for his own re-election campaign in May. Among the options open to the Electoral Commission is to refer both matters to the police.

South of the border, funding trouble was brewing for Tory leader David Cameron yesterday when it was disclosed that his constituency party had received more than £7000 in invalid donations.

The Witney Conservative Association has agreed to forfeit the sum to public funds because the benefactors were not on the UK electoral roll.

The news will be embarrassing for the Tory leader, who has been scathing in his criticism of Labour over the "proxy" donors scandal.

However, aides insist privately that the latest funding incident was the result of a "genuine mistake", and point out that Mr Cameron has stressed that errors will always occur at a local level. Records on the Electoral Commission website show that two donations received by the association on August 21 this year were subsequently found to have been impermissible. Roger Fletcher gave £5900, while Geoffrey Dobbs provided an auction prize worth £1500.

A total of £7400 was handed over to the Electoral Commission on November 16.

A Tory spokesman said: "As soon as we became aware that these two donations were not permissible we declared and voluntarily forfeited them to the Electoral Commission."

John Mann, Labour MP for Bassetlaw, said the revelation was "shocking".

"In recent weeks, we have heard Mr Cameron say someone who does not know what is going on in their party is not fit to lead the country. Presumably he believes that is even more true for someone who does not know what is going on in their own constituency office."

Meanwhile, a former minister has joined the Scottish Labour leader's team. Allan Wilson, who was a junior rural affairs and enterprise minister in the last administration, lost his Cunninghame North seat to the SNP's Kenny Gibson in May.

Yesterday, he began a three-month contract as a consultant in the Labour group's support unit with the remit of developing the party's policies in the run-up to their Scottish conference in March.

In particular, Mr Wilson will liaise with grassroots party members on plans for a constitutional commission to look at extra powers for the parliament. The move was voted through at Holyrood two weeks ago with the support of Labour, the Conservatives and the Liberal Democrats.

Writing in a Sunday newspaper last month, Allan Wilson said Labour had allowed itself "to be sucked into a constitutional quagmire" and should support an early independence referendum, which he said the unionist parties would win.

Speaking yesterday, Mr Wilson said: "People talk about powers for the parliament without any idea of what powers they're talking about. The idea of a constitutional commission is something I'm strongly in favour of. We've got to have a positive alternative to independence."

Mr Wilson refused to confirm or deny that he intends to stand as a candidate for Labour's general secretaryship in Scotland after Lesley Quinn steps down following the spring conference.