Simon Harris will be in an "impossible" position as Taoiseach, former Fine Gael minister Ivan Yates has said.
The new Fine Gael leader is expected to be confirmed as Taoiseach when the Dáil returns next week – with a Cabinet reshuffle his first order of business.
Simon Coveney has become the latest party member that will not be in the next Cabinet, after announcing he is stepping down as a Minister.
He follows Josepha Madigan who resigned her Junior Minister position last month.
Ivan told Newstalk Breakfast the changes give Simon Harris more options in his expected reshuffle.
"I was forecasting two weeks ago that I didn't see Simon Coveney in the next Cabinet simply because he only had one vacancy," he said.
"He has to have at least two at senior level and while he can take Helen McEntee out of Justice and make her a Super Junior, that is difficulty.
"The other difficulty is the other long-serving Minister is Paschal Donohoe, but that would give him three vacancies if he made a move in either of those directions.
"I think he faces a few serious questions".
'Facing in two directions'
Ivan said the new Taoiseach will be in an "impossible" position.
"He's got to provide Government stability, he's got to honour the Programme for Government and at the same time develop a new brand and image and be fairly strident as a new young leader of Fine Gael," he said.
"That's impossible, you can't face in two directions at the one time."
Ivan said he believes Mr Harris will also need to consider a very fundamental question.
When Simon gets space to think beyond the Programme for Government he's got to answer the question, ‘What is the difference between Fine Gael and Fianna Fáil?’" he said.
"To most people they both support the market economy."
'They can't afford houses'
Ivan said large cohorts of the population feel 'screwed over' by both parties.
"The difficulty both Fine Gael and Fianna Fáil face is under-35s believe their boomer generation screwed them over," he said.
"They can't afford houses, incomes haven't risen - 90% of people are under €70,000 a year - asking prices have risen a lot more and so therefore they are excluded from home ownership.
"Those people are moved to move [to] Sinn Féin.
"The second threat they face is the over-55s who would never vote for Sinn Féin or a left-wing party.
"What's going to emerge is the possibility in 43 constituencies that you could have 43 vibrant Independents of different views which will say, 'We'll put the local community before the party'".
Ivan said such an approach could make forming a Government in the next Dáil "a minefield".
Taoiseach Leo Varadkar announced his resignation two weeks ago.
Simon Harris was elected Fine Gael leader in his place four days later after he became the only person to be nominated.
