Peter Hain has apologised for other donations not being registered
Welsh Secretary Peter Hain said he is preparing a "full declaration" on donations made to him during the Labour deputy leadership campaign.
The Neath MP had already revealed a £5,000 donation had not been registered due to an "administrative error".
He has since admitted there were more donations that had not been declared. He is drawing up a list for the Electoral Commission.
The commission said "discussions were ongoing" with Mr Hain's office.
In April, a fundraising dinner for prominent Welsh businessmen was held as part of Mr Hain's deputy leadership campaign.
The dinner was paid for by Huw Roberts, a former aide to former Welsh Secretary Ron Davies.
Mr Roberts told BBC Wales he spent £1,300 to host the event, at the Park House Club in Cardiff on 23 April.
The contribution in kind was not declared by the Hain campaign.
In a statement on Monday evening, Mr Hain, who is also Work and Pensions Secretary, said: "In light of recent events I have undertaken a review of all donations to my deputy leadership campaign.
"This afternoon I have been to see the Electoral Commission to inform them that further donations to my campaign were not registered as they should have been."
"This is extremely regrettable and I apologise."
Mr Hain was one of six contenders for Labour's deputy leadership, which was eventually won by Harriet Harman. Around £77,000 was raised towards his campaign, according to the Electoral Commission.
Ms Harman has already pledged to pay back a £5,000 donation to her, successful, deputy leadership campaign.
She said she did not know the money, donated under the name Janet Kidd, was actually from property developer David Abrahams who is at the centre of a wider row over donations to the Labour Party.
Police are investigating more than £650,000 he donated to the party over four years, under the names of four associates.
Wayne David, Labour MP for Caerphilly, told BBC Radio Wales the non-declaration of donations was a "huge cock up" but there was "no question at all about Peter Hain being a man of integrity and transparent honesty".
"We are not talking about public money being mis-used, we are not talking about any sort of crooked dealings in terms of financial transactions. We are talking about transparency and of course the law is the law and it must be upheld.
"But it is very important to keep this in perspective."
Meanwhile, Sir Alistair Graham, former chairman of the Committee on Standards in Public Life, told BBC Radio Wales' Good Morning Wales programme the revelations that further donations to Mr Hain's campaign had not been declared were "disappointing".
He said the matter could now be taken up by the police and he was pleased that the Electoral Commission had moved quickly to report these matters to the police.
He said: "It's very disappointing when senior political figures, and particularly a cabinet minister from the government that introduced this legislation that he failed to comply with, don't go to the trouble of understanding what the rules are and making sure during a campaign that they comply with them.
'Totally honest man'
"I think it is doubly unfortunate that he announced a failure last week and then has taken it seems a fair old time to double check the records of his donations to find out that he failed to disclose some others as well.
"I don't think this puts senior politicians in a very good light."
Sir Alistair said he was pleased the Electoral Commission had produced a report to go to the police.
Don Touhig, Labour MP for Islwyn, said Mr Hain was determined clear up any discrepancies.
He told BBC Radio Wales that Mr Hain was known as a "totally honest man".
He said: "Peter Hain was not forced to do anything. Peter Hain volunteered the information when he found a discrepancy."