An honour nomination for a Labour donor was dealt with "in the normal way", the Cabinet Office has said after claims the Treasury pushed it through.
Police are investigating allegations of cash for honours
According to Channel 4 News, a "senior Whitehall insider" said officials did not want businessman Ronald Cohen to receive a knighthood.
Sir Ronald received the title for "services to the venture capital industry" in 2000.
The Tories said Chancellor Gordon Brown had to "come clean" about his role.
Sir Ronald is known to be a close friend of the chancellor.
Electoral Commission records show that Sir Ronald gave Labour £100,000 in 2001, £200,000 in 2002 and £250,000 in each of the next four years.
In the same year he received his knighthood, he was appointed by the Chancellor to head the Social Investment Task Force.
The Cabinet Office said: "There is an established process for making recommendations for honours.
"The recommendation for an award to Sir Ronald Cohen was made entirely in line with the normal process in the normal way."
The news report said the committee examining the submission thought Sir Ron deserved a lesser decoration such as a CBE, MBE or OBE.
Police are investigation allegations honours were given for cash. A report is due to be given to the Crown Prosecution Service in January.
Police have spoken to 90 people, including most of the Cabinet and former Conservative leader Michael Howard
Officers are also expected to speak to Prime Minister Tony Blair before concluding their inquiries but Downing Street has refused to comment on when an interview might take place.
The honours probe began after it was revealed the Labour Party was given secret loans ahead of the last election, and that some of those lenders had subsequently been nominated for peerages.
The inquiry has been widened to look at the other main parties.
The Conservatives said Mr Brown needed to "own up to the true extent of his role in the cash-for-honours scandal."
"It would be scandalous if the man who has his hands on our money had been forcing through an honour for his close friend and personal fundraiser.
The Scottish National Party, whose complaint prompted the inquiry, said involvement by Mr Brown "adds a whole new dimension to the cash for honours inquiry".
Alex Salmond said: "Up until now it has been assumed the prime minister was...in the frame because it was only he that could finally say whether somebody becomes a Lord or gets a knighthood.
"We have been assured the Chancellor has nothing to do with this, nothing to do with the fundraising, nothing to do with the award of honours.
"This story seems to drive a coach and horses through the Chancellor's alibi and as such will send shockwaves through Westminster."
Ninety people have been interviewed by police. All deny any wrongdoing.