NICK Clegg has rallied to the defence of Liberal Democrat cabinet colleague Danny Alexander over the donations row, sparked by a newspaper sting, insisting the Highland MP has done absolutely nothing wrong.

But the SNP, which is hoping to unseat the Chief Secretary to the Treasury in Inverness, Nairn, Badenoch and Strathspey, called for full disclosure in what it branded a "dodgy donation scandal".

Claims that a party fundraiser sought to bypass donation laws will cast something of a shadow over the Liberal Democrats three-day spring conference in Liverpool, which begins today.

The Deputy Prime Minister said any inference that Mr Alexander, who met a fake Indian entrepreneur and would-be donor in the undercover operation, had done anything wrong was "categorically untrue".

Mr Clegg insisted a recording supposedly revealing the Scot talking to the bogus businessman simply showed him being a "polite guy".

Mr Alexander, when told the fake entrepreneur had offered a donation of £7650 and had promised a further gift of up to £100,000, reportedly told him: "I just want you to know that I, personally, am very, very grateful for what you are doing and for what you are offering to do". He added: "I won't intrude on the details but, genuinely, it will make a difference."

It was claimed the bogus businessman was also introduced to figures such as Lord Ashdown, taken to Mr Clegg's office and attended a dinner for major party benefactors, where he met Mr Alexander.

The fund-raiser at the centre of the row, Ibrahim Taguri, has stepped down as the party candidate in Brent Central but will contest the Lib Dem seat as an independent.

It is alleged he told the bogus businessman that he could channel donations via family members and backdate cheques to avoid appearing on public registers. He was also said to have promised big donations could "open doors"

Official guidance, issued in 2007 in the wake of a scandal of "proxy" donations to Labour, says giving money via a third party "must not be used as an attempt to evade the controls on permissibility and transparency".

Lord Ashdown, the Lib Dems' General Election campaign chief, also insisted Mr Alexander had done nothing wrong but acknowledged Mr Taguri had "serious questions to answer".

The former party leader said the claim of trying to circumvent donations law was a "serious allegation and we are treating it very seriously" but he insisted the party had done "nothing illegal or improper".

Mr Taguri, who has stepped down as the Lib Dems' race equality champion, denied any wrongdoing and said he was "confident that I will be exonerated of all the claims made against me".

He confirmed he intended to fight the election as an independent but said he hoped to return to the party fold after clearing his name.

On his weekly radio phone-in, Mr Clegg said the undercover recording showed "Danny being a polite guy, just saying thank you to someone who he has been told is supporting the party".

The Lib Dem leader went on: "The idea that Danny or any parliamentarian has done anything wrong is categorically untrue.

"On the issue of Ibrahim Taguri, no cheque has been received by the Liberal Democrats, no cheque has been cashed. If we had received this cheque in question, of course it would have been scrutinised and checked."

But the SNP seized on the matter with Drew Hendry, its candidate seeking to unseat Mr Alexander, saying: "This latest episode is an extremely serious issue, apparently involving the Lib Dems at a very senior level seeking to break electoral law."

He went on: "Danny Alexander is at the centre of this dodgy donation scandal and he must provide an immediate and full account of his role in it. The people of Inverness, Nairn, Badenoch and Strathspey deserve full disclosure from Mr Alexander about this murky matter."

Mr Hendry added: "It seems the Lib Dems are becoming increasingly desperate to get their hands on cash regardless of where it is from."