WINDSOR, Ont. -- Ontario's NDP leader is dismissing a Liberal attack that alleges her party has a questionable financial relationship with a group of unions.

Andrea Horwath, who has been leading in recent polls ahead of next week's election, says her party has no financial relationship with the Cornerstone group.

She also says the governing Liberals made deals with special interest groups throughout their years in office.

The Liberals are calling on Horwath to disclose details of the NDP's links to the for-profit group founded by eight unions, alleging it is financially supporting the New Democrat election campaign and operations.

The attack comes after the Liberals have repeatedly gone after the NDP for their promise not to use back-to-work legislation if elected, saying Horwath would be beholden to unions.

The NDP says its lawyers are following up with the Liberals regarding their statements over Cornerstone.