Foreign affairs critic Paul Dewar levelled the widespread criticism at Baird during a news conference in Ottawa.
Dewar said an unprecedented strike by foreign service officers reflects badly on Baird.
"The Conservative government's refusal to bargain with Canada's own diplomats is a shameful injustice, not just for diplomats and their families but all Canadians and for Canada's reputation abroad," said Dewar.
Hundreds of foreign service officers have been without a contact for more than a year and a half. They have shut down some services at Foreign Affairs headquarters in Ottawa and at about a dozen missions abroad.
Dewar also blamed Baird for embarrassing Canada and souring relations with the United Nations by pulling out of various treaties or failing to honour others.
Baird's spokesman Rick Roth did not comment directly but took to Twitter to defend his boss.
"As with all public pronouncements that Paul Dewar makes, we'll have to wait a few days to see if his leader Thomas Mulcair smacks him down," Roth wrote, without explaining further.
Tory MP Andrew Saxton, the parliamentary secretary to Treasury Board Secretary Tony Clement, whose department is responsible for the foreign service negotiations, said the government has made a fair offer.
"These are very well paid positions. They come with great benefits, benefits that most Canadians could never even dream of. Private schools for their kids. Paid vacations to locations of their choice. They get cars shipped to them. They get their dry cleaning paid for."
The union and ex-diplomats say the benefits are intended to compensate foreign service officers for specific hardships. These include taking their spouses with them on postings where they might not be able to find work, or for living in a dangerous country or an expensive city they could not otherwise be able to afford on a Canadian salary.
The 1,350-member union has been without a contract since mid-2011 and has been in a legal strike position since April.
The union is trying to force Treasury Board to address a core grievance: that its members are paid as much as $14,000 a year less than their counterparts who do similar work in other federal departments.
Note to readers: This is a corrected story. An earlier version moved June 27 reported that Saxton said the government would not be tabling a new offer.
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