Fianna Fáil would retain state-imposed curbs on bankers' pay and bonuses if elected, the favourite to become Ireland's next finance minister has told Reuters.

Ireland capped executive pay at €500,000 a year during the euro zone's costliest banking rescue a decade ago.

It also banned all forms of variable pay and fringe benefits for even junior bank staff, restrictions lenders complain impedes them in attracting and retaining talent.

Fianna Fáil finance spokesman Michael McGrath said banks had to fully deal with the years-long mortgage overcharging scandal and parliament would have to introduce laws to make senior bankers accountable for such failings before he would consider the matter.

"It would be indefensible to lift caps and enable huge bonuses at a time when the banks are being investigated for misbehaviour," said the 43-year-old accountant, who is seeking re-election in Cork.

"We have had a history in the Irish banking system whereby bonuses were paid on the back of lending volume, much of it was inappropriate lending that never should have taken place. We have been badly burned and I think we have to tread very carefully."

McGrath said he would examine how Ireland's banks avail of corporation tax loss relief if he became finance minister but would not make any changes that would leave the state worse off by impacting the majority state-owned lenders' capital or value.

He said he would retain the €150 million annual levy paid by the banks at the current level.

McGrath, the main opposition finance spokesman in parliament since 2011, could be taking over the top job while new global rules are finalised into how multinational firms pay corporate tax - a direct threat to Ireland's low 12.5% rate that has helped attract some of the world's biggest companies.

Like the current government, Fianna Fáil would strongly oppose an EU-wide tax on big internet firms in favour of the global reforms being sought by the Organisation for Economic Cooperation and Development (OECD).

"We believe that fair tax competition needs to be protected and that's our bottom line going into any discussions. There is a veto at EU level, we would uphold that and not allow Ireland's corporate tax rate or regime be decided at EU level," he said.

"I believe that retaining a corporate tax advantage is imperative for Ireland. It is not the only reason why we have close to a quarter of a million people directly employed by multinationals but tax has been central to our success and to say otherwise would be misleading."

Fianna Fáil, which shares similar policies on Brexit and the economy with Fine Gael, has led in every opinion poll this year.

It hopes to form a coalition with smaller parties, but not Sinn Féin, whom it refuses to govern with.

Most analysts say another "confidence and supply" minority government deal with Fine Gael, this time with Fianna Fáil leading, is the most likely outcome. McGrath fears such an arrangement would struggle "to stand the test of time."

"On the current poll figures (forming a government) would be a challenge, for everyone," he said.