Conservatives leader Colin Craig has opened his wallet again to pour more than half a million dollars into his party's war chest.
Electoral Commission records showed Mr Craig, a millionaire property manager, made a $550,000 donation to his party earlier this week.
It brought his total donations to the party during this term to $721,000.
He has previously told the Herald that Conservatives planned to spend around $1 million this year ahead in campaigning for the September election, most of which would come from his own pocket.
In the 2011 election, he spent $1.6 million of his own money on campaigning.
Conservatives' total election spending of $1.8 million was the second-highest behind National but the party failed to win a seat.
Last week, Act co-founder and entrepreneur Alan Gibbs donated $100,000 to the party. The rich-lister has contributed around $400,000 to Act over several Parliamentary terms.
All party donations of more than $30,000 must be disclosed within 10 days.