Ontario Premier Kathleen Wynne will extend a ban on provincial politicians attending fundraising events to cover senior political staff.

Bowing to public pressure, Ms. Wynne tabled amendments on Wednesday that would toughen her proposed campaign-finance reforms to bar staffers from the Premier's Office or any party leader's office and the chiefs of staff of cabinet ministers from attending fundraisers. The bill already bars all MPPs and candidates from attending events.

Ms. Wynne said she decided to make the changes after receiving feedback during consultations on the legislation.

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"It's why we put the bill out for consultation after first reading and after second reading," she said in an interview. "So that there can be amendments to the legislation. This is the natural course of getting legislation right, and this is one of the final pieces we want to introduce."

The Premier brought in the reforms after a Globe and Mail investigation into cash-for-access fundraising. Under the system, corporate leaders and lobbyists seeking government contracts or policy decisions paid up to $10,000 apiece for exclusive face time with Ms. Wynne and members of her cabinet.

The bill is currently under review by a legislative committee, which is scheduled to vote on amendments next week. As the Liberals hold a majority of seats on the committee, Ms. Wynne will control which amendments get passed.

The plan is to have the legislation back to the House before the end of the current session in December for a vote, so it can be put in place on Jan. 1, 2017.

The amendments revealed on Wednesday would also grant an extra six months – until July 1, 2017 – to nomination contestants to comply with the fundraising ban. The government said it brought this in to make it easier for the chief electoral officer to get the administration of the new system in place.

The law will still allow politicians, including cabinet ministers, to fundraise over the phone or by e-mail.

Asked why she did not ban this as well, Ms. Wynne said it would be too onerous and that she is doing enough to curtail dubious fundraising practices as it is.

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"We've gone pretty far down that road. The reality is that ministers and members talk to all sorts of people and some of them give money and some of them don't," she said. "So I think that we've gone very far, we've gone farther than anyone else in the country in terms of delinking those functions, and I think we're in a much better place than we were six months ago."

The campaign-finance reforms would also ban corporate and union donations, cap total contributions from individual donors at $3,100 annually – compared with over $30,000 now – and place restrictions on super PAC-style third-party advertising groups that run attack ads against candidates.