By Steve Scherer and David Ljunggren

OTTAWA (Reuters) -Canadian Prime Minister Justin Trudeau is going to carry out a wide-ranging cabinet shuffle on Wednesday to focus on the economy at a time when the cost of living is a major issue for voters.

Trudeau, whose left-leaning Liberals have been in power since November 2015, will make the formal announcement at Rideau Hall, home to Governor General Mary Simon, the official representative of head of state King Charles.

New ministers will be sworn in at 10:30 a.m. (1430 GMT) and Trudeau will hold a press conference at 12:15 p.m., according to his official itinerary.

The Canadian prime minister looks set to leave heavy hitters such as Finance Minister Chrystia Freeland, Innovation Minister Francois-Philippe Champagne and Foreign Minister Melanie Joly in their cabinet portfolios.

Instead, in a shuffle of mainly second-tier ministers, he will seek to improve messaging on the economy at a time when the official opposition Conservatives are ahead in the polls.

"In the core economic files we are going to add more strength," a senior government source said on condition of anonymity. "The idea is to put new energy in key roles, and to put experienced people into new roles. When the time comes, they will be ready to hit the campaign trail."

The timing of the next election is unclear, since Trudeau commands only a parliamentary minority and relies on support from the left-of-center New Democrats to govern. That party has agreed to keep him in power until 2025, but the deal is not binding.

The right-of-center Conservatives blame what they call excessive government spending for high inflation and increasing complaints about unaffordable housing.

"We have a duty to avoid the danger that is coming for Canadian workers if we continue down Trudeau's path. Stop the inflationary spiral," Conservative leader Pierre Poilievre wrote on social media on Tuesday.

A Liberal source said Defence Minister Anita Anand was in the running to become head of the Treasury Board, which has overall control of government spending.

Ahead of the shuffle, four cabinet ministers said they would leave politics.

The Liberal source said Trudeau would ditch seven ministers. The Canadian Broadcasting Corp said they included Public Safety Minister Marco Mendicino and Justice Minister David Lametti.

(Reporting by David Ljunggren and Steve Scherer; editing by Paul Simao and Mark Heinrich)