Lord Saatchi has defended the charges for work done by his advertising company for the Conservative Party.
The Tories have been landed with a bill for the posters
He said fees levied by Immediate Sales, a subsidiary of M&C Saatchi plc, were "in line with industry practice".
Reports claimed the fees were £2.5m but Lord Saatchi's company disputed that saying there were only £769,000.
On Thursday a key Tory donor attacked Lord Saatchi for publicly criticising the party's general election campaign in pamphlet published after the poll.
Businessman Sir Tom Cowie said the party needed such criticism "like a hole in the head".
A statement issued by Lord Saatchi says that he worked for the Tories for no salary, no fees and no expenses for 18 months.
When the Australian political campaigner Lynton Crosby was appointed to run the Tory election effort, Lord Saatchi says he asked Michael Howard if he could become non-executive chairman rather than co-chairman of the party but the idea was rejected.
Mr Cowie, who donated £500,000 to the Conservatives ahead of the election, said he was not happy with paying for what ultimately turned out to be a failed advertising campaign.
He told BBC Radio 4's The World at One: "I would have thought, as a businessman, you only pay if you get success and not if you get failure."
But Lord Saatchi responded: "After the appointment of Lynton Crosby as campaign director after the last party conference I played no part in the briefings or approvals of Conservative advertisements."
Sir Tom Cowie was angered by Lord Saatchi's public criticisms of the election strategy.
The donor said: "I think criticism of this nature should be made to the people concerned, not to be publicly published in all of the newspapers. I think that is really working against the course."
He added: "As a party we need this criticism like a hole in the head."
The row came as senior figures in the party met to decide what leadership election options should be put to a ballot of party members, at the end of September.
Conservative MPs are suggesting that the system of selecting a leader is changed, so that they have the final say.
Currently the MPs select two candidates and ordinary party members vote on them.