The NSW Labor leadership battle is becoming "increasingly dirty" with a donation from a Chinese group linked to candidate Chris Minnsm the Kogarah MP.
Internal NSW Labor invoices obtained by the ABC showed Labor federal frontbencher Chris Bowen received a $100,000 donation from the Australian Chinese Teo Chew Association in April 2013.
From that donation, Mr Minns received a $5000 "moving expenses" payment to fund his return to Australia from the US, where he was studying at Princeton, to run Mr Bowen's election campaign.
Mr Bowen said yesterday the donation was "fully declared in accordance with the law", while Mr Minns denied knowledge of the source of the payment.
But several senior Labor sources said the emergence of the documents, which are understood to have existed within NSW Labor for six years, was timed to cause "damage" to Mr Minns.
Mr Minns is running against fellow Labor MP Jodi McKay for the leadership of the NSW party.
The Kogarah MP has a troubled relationship with the party's general secretary Kaila Murnain, who is understood to be backing Ms McKay for the leadership job.
Several sources said the campaign was "increasingly dirty" and a source from Mr Minns' campaign said it was inappropriate that his employment records "had entered the public domain".
"This an unfortunate development and concerning if this is going to be an indication of ongoing behaviour," a senior Labor source said.
Another senior source said: "This is an extraordinary intervention into a democratic process."
But a spokesman for NSW Labor said the party's head office had nothing to do with the release of the internal invoices.
"It is deeply disappointing that some have resorted to such low tactics and accusations. Party office encourages candidates to continue this contest in an open, positive and transparent manner," the spokesman said.
In a statement, Mr Minns said he had "no knowledge of, and has never seen, the documents" obtained by the ABC. He said in 2013, he had "no involvement in, or direct knowledge of Labor Party fundraising activity."
Mr Bowen said he welcomed Mr Minns' involvement in his re-election campaign in 2013.
"It was agreed between myself and the NSW party office that Mr Minns would run the McMahon campaign on his return from Princeton. I embraced this enthusiastically as Mr Minns is one of the best campaigners in the Labor Party," Mr Bowen said.
"I knew that he would be remunerated by the party office in accordance with guidelines and procedures both then and now."
