Opening a Commons debate on the findings of the Neill committee on standards in public life, the Home Secretary pledged that the Government was committed to introducing a ceiling of pounds 20m for each party's campaign spending atthe next general election.
However, while welcoming the report's main recommendations on party funding, Mr Straw renewed his criticism about the committee's call for the government of the day to remain neutral in a referendum campaign.
He said this was not the "clearest section" of the report and stressed that in some cases the Government would want to make sure not only that the issue was properly understood, but also that the Government's position was understood as well.
Eurosceptics are likely to seize on Mr Straw's reluctance to accept the report's key proposal to gain strength for their "No" campaign when a referendum on Britain's entry into the single currency is called.
Lord Neill's report, published last month, recommended an end to foreign donations and full public disclosure of donations of pounds 5,000, or more, to political parties as well as the spending cap.
Mr Straw said: "Here was a party of government which raised millions upon millions of pounds every year, yet persistently refused to tell the public where it got it from.
"Whether it was a pounds 1m gift from a Hong Kong businessman, here, or pounds 1.5m from a Greek shipping magnate, there, the Conservative Party's principal concern appeared to be the size of the cheque."
The shadow Home Secretary, Sir Norman Fowler, rejected the Home Secretary's attack on the Tories' reliance on foreign funds, stressing that the party's major donors would be listed in the annual accounts, to be published in the "next few weeks".
The Conservative party spent about pounds 28m on last year's general election campaign and the Labour Party spent pounds 26m.Reuse content