OTTAWA -- The parliamentary budget office says a pledge by the Trudeau Liberals to plant two billion trees could cost almost double what the government says.

The tree-planting spree, spread over a decade, is supposed to start in the spring and cost $3.16 billion over that time, based on federal estimates.

Getting to the 2030 target means planting about 200 million trees a year more than usual.

The spending watchdog's analysis suggests getting there is also going to require more money, about $2.78 billion more, bringing the overall cost closer to $5.94 billion.

The budget officer's report is based on a similar program the Ontario government ran, using the average per-tree cost and adjusting for inflation over the 10-year planting period.

The budget office also estimates in a separate report that a pandemic loan program for small businesses will cost the government nearly $20.3 billion, more than the $14.6 billion estimated in the fall economic statement.

This report by The Canadian Press was first published Jan. 28, 2021