OTTAWA — With Paul Martin's government still under fire for David Dingwall's expense claims at the Royal Canadian Mint, one of his ministers has sent a message to several Crown corporation chiefs: don't let it happen again.

Transport Minister Jean Lapierre has sent tough letters to the top executives at Crown corporations under his jurisdiction, The Canadian Press has learned. Citing "recent events surrounding the expenses and salaries of two CEOs of government-related corporations," Lapierre warns in one of the letters dated Oct. 17 that attention on them has been "heightened."

"The purpose of this letter is to remind you of the sensitivity of this issue and the need to operate within the limits of appropriate standards, guidelines, prudence and probity given that your organizations are public entities and therefore subject to public scrutiny," he says.

He asks for assurance that the chiefs and their boards of directors are being "vigilant" to prevent a repeat of the firestorm which has engulfed Dingwall, who resigned this month as head of the mint over his expense claims.

Another Liberal appointee, Andre Ouellet, has stalled for more than year in providing full receipts for some $2 million in expenses he billed over eight years as CEO at Canada Post.

Lapierre also asks in the letters that the chiefs promptly report to him "any special authorities granted by you or your board that may be viewed as problematic."

The reason, he notes in the wake of Dingwall's grilling by a parliamentary committee this past week, is that "I may be questioned, as shareholder of the Government of Canada, on the reasonableness of such authorities."