The venue — beside the centennial flame on Parliament Hill — was meant to be symbolic of the transparency and openness the Liberal leader hopes to bring to the way in which parliamentarians spend taxpayers' money.
But with clouds obscuring the sun, it seemed more emblematic of the current, opaque accounting of parliamentarian spending that Trudeau wants to fix.
"Sunshine is the best disinfectant," said Trudeau, who was nearly drowned out by the racket from nearby construction, a massive, noontime yoga class on the Hill lawn and a handful of Conservative protesters.
"And even though (the sun) didn't quite co-operate today, throughout my career, throughout the years going forward, a big piece of the Liberal party and of my own personal brand is openness and accessibility."
The Liberal leader said his "transformative" plan would make the expenses of parliamentarians more transparent than ever before — and make them more accountable for how they spend taxpayer dollars.
Trudeau acknowledged nothing in his plan would prevent "tremendous ethical lapses" such as improper housing allowance and expense claims by at least four senators, or the prime minister's chief of staff, Nigel Wright, personally giving $90,000 to Sen. Mike Duffy to reimburse his invalid expense claims.
There are already rules against those sorts of activities, he said.
But he contended the plan is a necessary step to restore Canadians' faith in public office holders, which has been badly shaken by the Senate expenses scandal.
His plan would require all MPs and senators to post online quarterly details of travel and hospitality expenses incurred by them and their staff, as cabinet ministers are already required to do.
Liberals will voluntarily begin posting their expenses in the fall, regardless of what other parties choose to do, he said.
But Trudeau's other proposals would require the support of other parties to implement:
— Opening up meetings of the secretive board of internal economy, which oversees House of Commons spending. This would require an amendment to the Parliament of Canada Act, which Trudeau said one of his MPs will propose in a private member's bill.
— Requiring detailed, easily accessible, online quarterly expense reports by all MPs and senators on how they spend their office budgets;
— Requiring performance audits of both houses of Parliament every three years by the auditor general and developing guidelines for when more in-depth, value-for-money audits should be conducted.
Treasury Board President Tony Clement welcomed Trudeau's proposals on behalf of the Conservative government.
"We are absolutely in favour of any measure that would have the same kind of expenses accountability that currently exists for ministers to be expanded to all MPs," Clement said.
"And we also have no difficulty opening up the board of internal economy."
Trudeau laid the blame for the Senate expenses scandal squarely on Prime Minister Stephen Harper and his "poor choices" for filling vacancies in the chamber. He said a Liberal government would implement a more independent process for advising the prime minister on Senate appointments — much as is done for judicial appointments.
Trudeau's initiative came shortly before the House of Commons began debating an NDP motion aimed at financially starving the Senate. The motion was defeated late Wednesday, with Conservatives and Liberals voting against. Trudeau had earlier dismissed the motion, which would cut off funding to the Senate as of July 1, as a "political game."
But NDP Leader Tom Mulcair argued that abolition of the Senate is the only real way to resolve the expenses scandal, which he said derives from the fact that the chamber is unelected, unaccountable and stacked with Liberal and Conservative party "hacks, bagmen and fundraisers."
"We're not about to start talking about reforming something that can't be reformed," Mulcair said.
He resisted suggestions that MPs' expenses should be scrutinized by the auditor general, as the government wants to do for senators' expenses.
Auditor general Michael Ferguson last year reported on administrative procedures in both houses of Parliament, Mulcair noted. While Ferguson found numerous problems with the lack of controls to ward against improper expense claims in the Senate, Mulcair said he gave the House of Commons a "clean bill of health."
However, the auditor general has never conducted a detailed, comprehensive audit of individual parliamentarians' expenses.
A motion by government Senate Leader Marjory LeBreton, calling on Ferguson to conduct just such an audit of Senate expenses, got bogged down Wednesday amid concerns from some of LeBreton's own Conservative colleagues.
Sen. Pierre Claude Nolin said he'll support the motion. Nevertheless, the Tory senator raised concerns that the motion constitutes an attack on the Senate's legal authority to administer its own business.
"I do not want us, and those in the future who will analyse the decision that we are about to take, to think that we are abdicating privileges we have to administer ourselves, our institution," Nolin told the Senate.
"No one else has that authority."
Several senators suggested the motion may need to be amended, making it clear that the internal economy committee, which oversees the chamber's administration, is inviting Ferguson to conduct an audit and could set parameters for it — precisely what LeBreton has said was wrong with previous audits.
Another Conservative senator, Jean-Guy Dagenais, signalled his displeasure with adding one more layer of scrutiny to senators' expenses, which have already been examined by the internal economy committee and an outside auditor and are under review by parliamentary ethics officers and even the RCMP.
"Now we're adding the auditor general," he groused after emerging from a Conservative caucus meeting.
"Right now, we're putting pressure on sitting senators who are doing their job and who are honest. Now we're starting to get fed up."
Liberal senators, whom Harper accused Tuesday of blocking LeBreton's motion, signalled their support for it, although they dubbed it little more than a distraction aimed at diverting attention from the explosive Wright-Duffy transaction.
"Let us adopt it, get rid of it and return to the serious issue of what Canadians see as hush money flowing from the office of the prime minister of Canada to a sitting parliamentarian," said Liberal Senate Leader James Cowan.
Debate on LeBreton's motion was adjourned until Thursday.