Two more senators are leaving their caucuses to join the upstart Canadian Senators Group — with Conservative Quebec Sen. Jean-Guy Dagenais citing his discontent with Andrew Scheer's leadership as the reason for his defection.

The other defector, P.E.I. Sen. Percy Downe, is also joining the CSG — only days after he agreed to disband the Senate Liberal caucus and sit with his former colleagues as a member of the Progressive Senate Group.

Dagenais said Monday that Scheer disappointed in the last federal election. He argued Scheer's social conservatism on issues such as same-sex marriage and abortion torpedoed the party's fortunes in Quebec.

Dagenais said he made up his mind to leave the Conservative Senate caucus after sitting through the party's election post-mortem meeting, which saw members discuss what went wrong with the party's campaign strategy.

Beyond the leader's stance on contentious social issues, Dagenais said Scheer attached a "low importance" to Quebec and he could no longer sit as a member of his caucus as a result.

"We have wasted a unique opportunity and the result will be the same the next time if the current leader and those who advise him remain in office, as is the case at this time," Dagenais said in a statement.

Downe's departure puts the days-old Progressive Senate Group's future in jeopardy. The number of Progressive caucus members has now dipped below the threshold for a "recognized" group or caucus in the upper house.

The two departures come as Canada's upper house is in a state of flux. Prime Minister Justin Trudeau's push to rid the Senate of partisanship through the appointment of Independent senators has effectively dismantled the Liberal and Conservative duopoly that has long dominated the Red Chamber.

Trudeau's re-election suggests his reforms are set to take on a more permanent form — which has pushed some senators to shed their party stripes.

'Very disappointed'

The CSG is a group of former Conservative and Independent senators, most them conservative-leaning parliamentarians appointed by former prime minister Stephen Harper. With the two additions, the CSG now has 13 members.

Speaking to CBC News Monday, interim Progressive Senate Group Leader Joseph Day said he was "very surprised and very disappointed" to learn of Downe's abrupt departure for a right-leaning group like the CSG.

"He knew absolutely everything we were doing last Thursday in terms of launching our new group and he saw fit to resign from the group that evening," Day said.

Sen. Joseph Day speaks to media in Ottawa. The Liberal caucus formally disbanded today to create a new group called the Progressive Senate Group in an effort to attract new progressive-minded senators. (Adrian Wyld/Canadian Press)

"We've been together 15 years. For him to make that decision without consultation with me, as the leader of the group, or any of the other members of our group, was surprising for someone of his political background. Very surprising and very disappointing."

Before his appointment to the Senate in 2003, Downe served as chief of staff to former prime minister Jean Chrétien.

Day said the members of the Progressive Senate Group describe themselves "as centre-left ... I think that's exactly where all our members are and we feel very comfortable there and (Downe) didn't."

Reached by phone Monday, Downe said he was proud to see the Liberal Senate group hold on for so long after Trudeau ejected its members from the national Liberal caucus in 2014.

He said the rebrand last week — disbanding the Liberal caucus and creating the new Progressive group — didn't sit right with him.

"The end of the Liberals was the difficult part for me," he said.

He said he still supports the Liberal Party of Canada. "Like the cheques I wrote in the last federal election, I'll continue to do that in the future. The CSG allows for that freedom — the new group has no restrictions on political activity."

Downe said he suggested months ago that the Liberal caucus take steps to grow its membership in order to avoid the fate it faces now: extinction due to retirements and defections.

"If we were going to wrap it up as a Liberal group in the spring, there could have been opportunities to expand," he said.

He said the radical rearrangement of the Senate along non-partisan lines has now presented him with a chance to make an affiliation change. Downe said he likes the "diversity of views" in the CSG, given that the group is composed of senators appointed by former prime ministers Paul Martin, Harper and Chrétien.

Progressive group set to lose funding

Under Senate rules, a group or a caucus must have at least nine members to be considered "recognized" — a designation that gives a group extra funding for staff and research. With Downe gone, the Progressive Senate Group has just eight members.

Downe's defection, paired with two upcoming retirements early in the new year, means the caucus likely will lose its $410,000 in annual funding at the end of this fiscal year.

Downe's switch also could put Progressive seats on committees in jeopardy, as the group no longer has any official standing in the chamber. Most of the Senate's "sober second thought" function happens at committee meetings and committee seats are prized by members of the upper house.

Despite the disruption, Day said the Progressive Senate Group will carry on and will fight for funding and committee seats when Parliament returns in December.

He said the group is not disbanding and members will continue to identify as Progressive senators even if the Senate's website now classifies the senators as "non-affiliated."

The addition of new recruits would save the Progressives from folding.

"I just know that if we can demonstrate that we can continue as cohesive group, we will have others joining our group of like minded-senators," Day said.

When asked what message he'd send to former colleagues, Downe said, "I don't really have a message for them. There's a lot of change in the Senate. They have identified a number of people they're interested in so ... it's too early to say [what their future will be]."