OTTAWA - The federal government has issued a scathing letter aimed at Ontario Premier Dalton McGuinty.

The Conservative government defended its plan to add 22 seats to the House of Commons and rebutted the premier's claim that it shortchanges Ontario.

The letter from Tory House leader Peter Van Loan accuses the Liberal premier of a partisan attack.

It goes on to suggest that the newly elected McGuinty doesn't even understand the legislation.

Under the bill, Ontario would get 10 new seats in the House of Commons; other fast-growing provinces -- B.C. and Alberta -- will get seven and five seats, respectively, to reflect their population growth.

McGuinty points out that the bill would still leave Ontario with slightly more voters per riding than elsewhere in the country.

But Van Loan retorts that the bill McGuinty's complaining about actually takes steps to correct the problem.

The federal bill must be passed in Parliament, and new riding boundaries would be redrawn by non-partisan committees in each province, before the changes kick in by 2011.