Latest figures for 2004 have revealed that Intermediate Sales Company and M&C Saatchi charged the Conservatives 拢339,000 and 拢207,000 respectively.
According to The Times, a further 拢1m was charged during 2005 before the General Election.
A Conservative Party spokeswoman said: "We can confirm that the figures for 2004 are accurate but we can not comment on any figures for 2005 as we have not finished the accounts for this year."
Lord Saatchi quit as co-chairman of the Conservative Party following the election defeat and publicly criticised the campaign afterwards.
According to media reports, he was unhappy with the focus on issues such as immigration and said the campaign had treated the public like "morons". He also blamed himself for his role in the defeat.
News of the charges comes as the party considers moving back into its old Smith Square headquarters, after it failed to sell the building having moved out two years ago.
The party is deep in debt, owing a reported 拢12m in loans.
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