Boris Johnson has been blocked by Ruth Davidson from attending the Scottish Conservative party conference in Aberdeen this weekend.

Scottish Tory sources said a number of potential leadership candidates had been “discouraged” from attending the event, which begins on Friday, amid concerns their appearance could distract from party leader Davidson’s return from maternity leave, insisting the decision was not personal.

Davidson appeared to downplay Johnson’s chances of success in any leadership contest in an interview on STV’s Scotland Tonight on Thursday night. She said: “Let’s remember that not everyone people talk about being a frontrunner make it to the starting line: Boris didn’t last time.”

Scottish Tories are understood to have profound concerns about the unpopularity of a Johnson leadership at Westminster with voters north of the border, and Davidson herself has regularly called out his disruptive behaviour over Brexit.

Sources close to Davidson said they did not want the two-day conference to turn into a leadership hustings when the focus should be on Davidson’s return to frontline politics and the launch of a two-year campaign to elect a Tory government to Holyrood in 2021.

Asked on STV about the presence of Michael Gove and Sajid Javid at the conference – Esther McVey will also appear at a fringe event – Davidson said: “There’s a lot of people want to appear at our conference.”

While reiterating her “full support” for Theresa May, Davidson added that she would assess of all of the leadership candidates according to three criteria: their ability to strengthen the union, advance Scotland’s priorities, and bring the whole of the UK back together after Brexit.

Gove, who will address the conference on Saturday morning and speak at a dinner the previous night, is regularly cited by senior Scottish Tories as a politician who “gets the union”. Last May, Gove and Davidson backed the launch of a thinktank aimed at appealing to a new generation of Conservative voters.

The Telegraph reports this morning that Johnson had originally scheduled to travel to Aberdeen to campaign with the local MP Ross Thomson last week but was advised by Davidson to delay the visit until after the conference.