He claimed it was a bid by Labour to "screw the scrum" to penalise Act and National.
He said if the 225 donors who gave $5,000-$15,000 in 2020 dropped their donations to less than $5000 to avoid being named, it would knock $1.2 million off the amount that had gone to political parties. Act would be down about $300,000 and National almost $600,000 while Labour, which got far fewer donations, would lose $170,000.
Seymour disputed donations of less than $15,000 would buy influence, saying it amounted to less than one per cent of the funding needed to pay for a campaign.
"Nobody can get undue influence over a political party for funding one per cent of a campaign.
"Without donors, our democracy would not function, but they are being made out to be something sinister."
He also criticised the timing, coinciding with the start of the High Court hearing of charges of fraud relating to donations to National and Labour.
"It would have been more respectful of comity with the Courts to have left this legislation until after these high-profile cases, affecting parties voting on the legislation, had concluded."
Act and National have this year undertaken major fundraising drives among rich-listers, which have so far secured National about $2m and Act about $1m – amounts which do not include any donations of less than $30,000.
Allan said it had to go before Parliament now to ensure there was time for public submissions and to pass before the end of the year, in time to take effect before the 2023 election.
However, National's justice spokesman Paul Goldsmith said changes to electoral laws should be done with cross-party consensus and broad public consultation – rather than be rammed through.
"The broad purpose is to make it more difficult for political parties to raise funds.
"The objective of this Government is clear, which is to push us toward taxpayer funding of political parties and we don't agree with that."
He said there was no evidence that lowering the limit from $15,000 to $5000 would have any impact, or that donations of up to $15,000 had had any undue influence on a party.
Green Party electoral reform spokeswoman Golriz Ghahraman called for the reforms to go further, and for the bill to be used for an urgent fix to the "loophole" exposed by the recent court case on the NZ First Foundation.
The High Court acquitted two people on charges over donations to the Foundation which had not been disclosed, saying they did not fall foul of electoral laws because they were not considered party donations.
The Serious Fraud Office is yet to say whether it will appeal against that decision.
Ghahraman said it exposed a loophole which needed to be closed quickly and electoral experts had pointed to steps that could be taken to do so.
Prime Minister Jacinda Ardern has said it could be considered as part of the broader longer review of electoral laws, but it was unlikely it could be addressed in time for the 2023 election.
