Scottish politics is being "degraded" by "an orchestrated campaign" to drag down Wendy Alexander and other Labour politicians over money and fund-raising.

A spokesman for the Scottish Labour leader made the claims in response to more revelations about fund-raising for her Paisley constituency.

Another Labour MSP, Deputy Presiding Officer Trish Godman, yesterday defended her financial affairs in connection with her son, who faces three years in a US jail for fraud. "I make no apology for standing by my son while he was awaiting trial in America," she said.

Ms Alexander was accused in a Sunday newspaper of failing to declare a £900 donation from an education company when she bowled a soft question in a committee hearing to a company representative.

She was further attacked over a Scottish Industry Forum dinner six years ago, in which participants, including STV journalist Bernard Ponsonby, have since claimed they were not told of its Labour fund-raising link.

A spokesman for Ms Alexander said the donation had been registered and no other MSP had declared a party donation during debate within the Scottish Parliament, including Alex Salmond when recently quizzed about an Aviemore hotel planning application by a SNP donor.

He said that anyone who knows Mr Ponsonby would "fall over laughing at the idea he had been duped or misled".

"There is a politically-motivated campaign being orchestrated against Wendy Alexander, and being pursued by the SNP," said the spokesman. "It is degrading Scottish politics."

Mrs Godman faced Sunday paper allegations about her purchase of a £250,000 Edinburgh flat from her financier son Gary Mulgrew, who was jailed for 37 months last week in Texas for offences linked to the Enron scandal.

The Renfrewshire West Labour MSP said her son, 45, required the money to pay legal costs. With her husband, a former MP, she had complied with the "appropriate regulations", and bought the flat at market value in October 2006.