Ireland will back keeping Britain in the single market, even if the country votes to leave the European Union next week, Michael Noonan said in Luxembourg.
Opening the door to a post-Brexit free-trade deal while the UK vote hangs in the balance runs the risk of making British prime minister David Cameron's effort to shore up faltering support for the 'Remain' side even harder.
Mr Cameron's campaign is focused on highlighting the risk to Britain of quitting the EU, especially the possible loss of access to the common market.
However, Mr Noonan yesterday played down the tough comments from Germany's Wolfgang Schauble, who had said the UK would be locked out of the common trade area if the Brexit vote was carried.
With less than a week to go until the vote, Mr Noonan said Ireland was "unashamedly" of the view that Britain must remain part of the EU.
And he predicted that UK voters would ultimately choose to remain in the bloc, despite opinion polls suggesting momentum for the 'Leave' camp.
Germany's finance minister Wolfgang Schauble has warned that a vote next Thursday to leave the EU would mean that Britain would not be able to continue to benefit from the single market as Norway and Switzerland do.
"What Mr Schauble says is legally and technically correct, but I don't think it is the end position," Mr Noonan told the Irish Independent, ahead of a meeting of eurozone finance ministers in Luxembourg.
He said Ireland would be in favour of allowing the UK single market access because of the important trade relationship between Britain and Ireland.
Ireland would also want to ensure the retention of the common travel area between this country and the UK if Britain quit the EU.
But Mr Noonan warned that there were no guarantees.
"There is a two-year period to make any alternative arrangements, but the fact that they leave means they leave," he said.
"You can't be half in or half out. If they leave, they leave, but then they'll have to negotiate an alternative arrangement. I presume a single market (access) would be one of their top priorities in any future arrangement."
Asked if Ireland would support the UK being allowed to remain in the single market, Mr Noonan replied: "We would, of course, because they are our biggest trading partners and we don't want any impositions to trade between the two islands."
Opinion polls suggest that the Leave side is now ahead in the UK.
A survey by Ipsos MORI for the 'Evening Standard' newspaper, released yesterday, showed 53pc support for Leave and 47pc for Remain, excluding the 'don't knows'.
Mr Noonan said he believed that UK voters would ultimately vote to stay.
"I think it's very close. I think it's too close to call but I still have a feeling that the voters in the UK will vote to stay in," he said.
The Finance Minister also suggested he wasn't concerned at this stage about the impact that the vote was having on Ireland's borrowing costs, which have been inching up as investors grow increasingly jittery.
"There's going to be some movement, but the movement doesn't seem to be dramatic yet," he said. "While we have contingency plans, they're not refined down to the last detail because we don't know what the detail will be."