OTTAWA -- Justin Trudeau is extending the terms of the federal ethics and lobbying watchdogs by another six months and relaunching the application process to find their replacements.

It's the third time the prime minister has given six-month extensions to ethics commissioner Mary Dawson and lobbying commissioner Karen Shepherd, both of whom were scheduled to leave their posts within the next few weeks.

The move underscores the difficulty the Trudeau government has had in finding replacements for officers of Parliament, the watchdogs who are supposed to provide independent oversight over crucial matters like federal elections, government spending, ethics, lobbying, linguistic duality and access to information.

And it comes on the heels of Trudeau's botched nomination of Madeleine Meilleur, a Liberal partisan and former Ontario cabinet minister, to the post of official languages commissioner.

Meilleur withdrew her nomination Wednesday after weeks of controversy over her partisan ties to the very government she was supposed to hold to account and amid opposition complaints that they weren't consulted, as legally required for an officer of Parliament.

A senior government source told The Canadian Press that Trudeau will send letters next week to opposition leaders, asking them what stakeholders they want consulted about the next ethics and lobbying commissioners and urging them to encourage potential candidates to apply.

The government posted online Friday a new "notice of opportunity," inviting applications for the two posts.

In the meantime, Privy Council Office spokesman Paul Duchesne confirmed that Dawson and Shepherd, whose terms were originally supposed to expire a year ago, have agreed to serve until the end of this year.

Since taking office, Trudeau has had the opportunity to choose successors for five of the eight officers of Parliament -- all but the auditor general and privacy and public sector integrity commissioners. So far, he's filled none of those slots.

In addition to Dawson and Shepherd, he's extended the term of information commissioner Suzanne Legault, which was to end this month, until the end of the year.

The post of chief electoral officer has been vacant since Marc Mayrand retired in December. Mayrand gave advance notice last June of his intention to step down precisely because he believed "the early appointment of a successor to lead Elections Canada well ahead of the next general election (in 2019) is essential and should not be delayed."

The official languages slot has also been vacant for six months and is likely to remain so for some time now that Meilleur has withdrawn.

The delay in finding timely replacements for Dawson and Shepherd has complicated the selection process, since both their offices are now immersed in investigations involving Trudeau himself. Shepherd has been examining the involvement of lobbyists at fundraisers featuring the prime minister and Dawson has been examining Trudeau's use of a private helicopter during a family vacation last Christmas to the private Bahamian island owned by the Aga Khan.

Trudeau has recused himself from choosing Dawson's replacement to avoid the appearance of a conflict of interest. He has not recused himself from the choice of a new lobbying commissioner.

In part, the delay is due to the new process Trudeau has initiated for filling vacancies in some 1,500 so-called governor-in-council positions, including officers of Parliament. It is supposed to be more transparent, merit-based and open -- with vacancies posted online and Canadians invited to apply -- and more reflective of the country's diversity.

But it's also turned out to be more time-consuming.

"The more rigorous approach to conducting selection processes represents a significant volume of work," said Duchesne, adding that more than 14,000 applications have been received since the new process was launched last year.

In the Commons on Friday, government House leader Bardish Chagger boasted that more than 150 appointments have been made under the new process, 60 per cent of whom are women, 13 per cent visible minorities and 10 per cent indigenous Canadians.

However, the senior government source, who was not authorized to speak publicly on the matter, acknowledged that finding officers of Parliament has posed a particular challenge. In part, that's because the specific qualifications for each watchdog are spelled out in legislation, resulting in a pool of candidates that is "naturally quite small."

Moreover, because the watchdogs tend to play highly visible, public roles -- and have faced harsh criticism in some instances -- the pool of candidates willing to take on the jobs is whittled down even further, the source said.

But Duff Conacher, founder of the non-partisan, ethics advocacy group, Democracy Watch, disputed that contention. The statutory qualifications required for most of the watchdog posts are very broad or non-existent, he said.

His group has repeatedly called on the government to create a truly independent appointments commission, as has been done in Britain, and is about to launch an online petition to "stop political lapdog appointments."

Conservative deputy ethics critic John Brassard accused the government of deliberately stalling appointments to other watchdog posts while it floated the Meilleur "trial balloon" to see if it could get away with partisan appointments to what are supposed to be non-partisan positions.

"Parliament is not a Liberal partisan playground," Brassard told the Commons, asking, "When will the prime minister put down the selfie stick and get to work by appointing independent, non-partisan officers of Parliament?"

Echoing Trudeau's defence of the Meilleur appointment, Chagger continued to argue that past political involvement shouldn't automatically disqualify an otherwise qualified person from appointment to a watchdog role.

"That's simply wrong," retorted Conservative MP Kevin Sorenson. "No one believes that people giving tens of thousands of dollars to the Liberal party are independent."