TORONTO - The NDP say the governing Liberals didn't tell the public about safety concerns with girders used in the Windsor parkway until they thought it would land on the front pages during a byelection.

The New Democrats say documents show that Premier Kathleen Wynne came clean in July, 2013 when Ministry of Transportation staff suspected that The Windsor Star would break the story during her campaign stop in the city.

They say the documents also show that the ministry staff had discussed the problem internally since late 2012.

An expert panel later appointed by the government questioned the durability and safety of hundreds of support beams used in the construction of the $1.4-billion Windsor parkway.

The panel found that tack welding was used in assembling the girders, which violates federal code.

The company responsible for the parkway project has promised to replace 508 of the 562 concrete girders identified by the panel at no cost to the province.