Prime Minister Mark Carney has been unable to find a permanent chief of staff, and is keeping former cabinet minister Marco Mendicino in the government’s top political job only until the end of June, two sources say.

A number of senior Liberals, including Justin Trudeau’s former principal secretary Gerald Butts, veteran ministerial chief of staff Cyrus Reporter and former United Nations ambassador Marc-André Blanchard, were approached to take on the job but declined, according to the sources.

Mr. Carney has since decided to keep Mr. Mendicino as interim chief of staff until the end of the June parliamentary session as the search continues for someone with the breadth of experience to handle the position‘s onerous responsibilities.

The Globe and Mail is not identifying the two sources, who were not authorized to discuss internal staffing.

In a statement on social media late Thursday, Mr. Carney said he asked Mr. Mendicino to remain as his top manager in the Prime Minister’s Office through the busy month ahead.

“As we prepare for the Throne Speech, I have asked Mr. Mendicino to stay into the summer in order to support the launch of the government’s mandate in Parliament and to lead the transition of the PMO on my behalf. I am grateful that he has agreed to do so,” he said.

Mr. Carney made no mention of when he would name a full-time chief of staff. He tweeted the statement after The Globe made inquiries about Mr. Mendicino leaving the PMO this summer.

The position of permanent chief of staff is one of the most important jobs in politics. A chief of staff provides stability, particularly for a government with a new leader and an ambitious agenda. The individual has great influence over ministers, caucus and the bureaucracy, as both a motivator and an enforcer of government policy.

One of the two sources said that Mathieu Bouchard, a former top adviser to Mr. Trudeau, has not ruled out taking on the job.

Tom Pitfield, who oversaw the Liberal election campaign along with Mr. Butts and campaign manager Andrew Bevan, is interim principal secretary but he is also not expected to stay past June.

The government has also begun selecting chiefs of staff for cabinet ministers, the sources said, and those names are expected to be released next week. The list is being overseen by the PMO.

The lack of a permanent chief of staff makes it difficult to permanently fill top positions in the PMO, as a number of senior people, such as foreign-policy adviser Scott Gilmore, only signed on for short-term stints until the election was over. Other experienced Liberals may not wish to join the PMO until they know who they will be working under as chief of staff.

One of the Prime Minister’s conditions is that he wants a chief of staff who would be willing to serve for several years in a job that is quite demanding, the sources said.

“It is really a 24-7 job,” said Senator Percy Downe, who served as chief of staff to former prime minister Jean Chrétien.

“They are an extension of the prime minister, so when they pick up the phone and call somebody, they are not calling for a chat. They are calling for a specific purpose, which is to move the government’s agenda, to correct any errors that a minister may have made and to get them back on track on what the prime minister ran on in the election.”

The two sources noted that the lack of a strong chief of staff was evident last week when several ministers spoke on issues that had nothing to do with their portfolios.

Canadian Identity Minister Steven Guilbeault, for example, told reporters that there was no need for additional oil pipelines because the Trans Mountain pipeline is working under capacity. His comments caused a stir in Western Canada, particularly from Alberta Premier Danielle Smith and Saskatchewan Premier Scott Moe.

A key job of the chief of staff is to make sure the federal bureaucracy implements the government’s agenda.

“Those items that the public service supports in the government’s platform will be enthusiastically endorsed and implemented,” Mr. Downe said. “Those items that they may not be as keen on require the PMO, working with the minister, to implement a bring forward list: ‘Where are we on that? Have the target dates been met? If not, why not?’ ”

The chief of staff also advises ministers on proposals that could have a negative political impact in various regions of the country.

The chief of staff and Clerk of the Privy Council, the top bureaucrat, sit in on cabinet meetings along with the prime minister. Usually, the chief of staff is not allowed to attend national caucus meetings.

Under Mr. Trudeau, however, chief of staff Katie Telford attended caucus meetings, which Mr. Downe said he thought was unwise as it inhibits MPs from speaking out.

Under Mr. Chrétien, no staff were allowed into caucus so MPs and senators could freely tell the prime minister what they thought the government was doing well or badly.

Mr. Downe said he would be debriefed on what went on by the national caucus chair, who would never share names of MPs who were critical of the government.

“So people felt free to speak and their comments either positively or negative would come to me but I would not know who said them,” he said.