New Progressive Conservative Leader Patrick Brown won't get a chance to seek a seat in the Ontario legislature before the fall session begins Sept. 14.

Premier Kathleen Wynne rejected a request from Brown on Thursday for an immediate byelection in Simcoe North, where veteran Tory MPP Garfield Dunlop announced he would step aside Aug. 1 so the new PC leader could run for a seat.

Wynne insisted she was "keen to let Brown have his shot" at winning a seat in the legislature, but said she would wait until after the Oct. 19 federal election before calling the provincial byelection.

"The fact is, now, we don't know exactly when the federal government is going to drop the writ or is going to call the federal election," she said. "We know when it's going to be, but we don't know how long the writ period will be."

Brown resigned his seat in Parliament as the MP for Barrie after he won the provincial PC leadership in May, and Wynne said at the time she would call a byelection "as soon as he can find a riding" in which to run.

Brown waited too long to find that riding, Wynne suggested Thursday.

"When he went through the leadership process, and I said right away I'm not going to stand in the way of a byelection, I didn't think he would be waiting three months to decide that he wanted to come in to the house," she said.

Wynne also said there is not enough time between Dunlop's resignation date and the start of the federal election campaign to file all the necessary paperwork and hold a byelection in Simcoe North, which borders on the Barrie riding. "It's actually impossible now, given the period, to have a byelection in August," she said.

Brown wrote an open letter to Wynne urging her to schedule the byelection in August so he could be in the legislature in time for the fall session.

"If you truly believe that your government's ideas will be good for our province as you claim, you should be open to having me in the legislature as leader of the official Opposition, asking you questions come September," wrote Brown. "I urge you do the right thing. Ontarians don't need political games."

Brown also said the Simcoe North byelection could be completed before the federal election is "significantly underway."

Deputy Premier Deb Matthews wrote a letter to Brown late Thursday blaming the Conservatives and their new leader for taking too long to seek a byelection.

"Your party chose to delay for months and you repeatedly stated only that you intended to enter the house in 2018," wrote Matthews. "I was surprised at your proposal to call a provincial byelection in the middle of the federal election campaign, which could deny the voters of Simcoe North a fair election and the opportunity to properly consider all candidates."