A former gang member-turned opera singer has corroborated Manukau Mayor Len Brown's explanation for an $810 dinner at a Manurewa restaurant last September.

Geoff Knight said yesterday that he had performed at Volare Restaurant to raise money to support a move to Australia for music lessons.

Speaking from the Gold Coast where he is now based, Mr Knight said: "Man it was a great opportunity for me to work a room of businesspeople and others and I wasn't shy."

Mr Brown's opponents have questioned whether the dinner was a genuine business expense and criticised him for not declaring who was at the event or providing an itemised account, which are required under the council's credit card policy.

Mr Brown has admitted to not providing a tax invoice and itemised account, but refused, for privacy reasons, to say who he entertained that night. However, he has explained the dinner in general terms as "a fundraiser in support of a young singing artist in our community" for which the council bought a table.

Mr Knight, who has gone from being a member of the Highway 61 motorcycle gang in Manukau to an opera singer, said it was a successful evening.

"Daniel [Nahkle, the restaurant owner] paid me a reduced fee as agreed, also gave me a small donation as he thought I was extremely talented and I also got some investment commitment on the night and some good contacts," he said.

Mr Knight has also performed at the Manukau Festival of the Arts in 2008, free at Mayoress Shan Inglis' Charity Gala Ball in May this year that raised $170,000 for Kidz First Children's Hospital at Middlemore and the week prior visited eight South Auckland schools to sing and tell his story.

Mr Nahkle confirmed that the evening, which had an opera theme and cost $70 a head, had been held to enable Mr Knight to raise money to head to Australia for some coaching.

He said it was not possible for the restaurant to provide an itemised account after the account had been closed off. Mr Brown paid for his table's dinner with his credit card and obtained an eftpos receipt.

The council did not get a tax invoice from the restaurant until after Mr Brown's credit card spending became public and Audit New Zealand told the council tax invoices were missing on some credit card transactions.

The Volare dinner is one of several credit card transactions Mr Brown has had to defend over the past two weeks. He has admitted using his council credit card to make four personal purchases, including a $148 mini hi-fi system and $59 Christmas ham. He had repaid the council for personal spending totalling $638.27.