Lord Heseltine has told ITV News he would be "torn" if faced with the choice of backing a Labour government that wanted to reverse Brexit.
The former Conservative Cabinet minister earlier faced calls to have the party whip withdrawn, amid accusations he is attempting to "sabotage" Brexit.
But he confirmed to ITV News that if supporting a Labour government would bring a halt to the UK's move to leave the EU he would find his loyalties divided.
In practice, the Tory grandee would have no vote to give a Labour government as he sits in the House of Lords.
But speaking hypothetically he said: "I am torn, because I realise the enormous damage that both these options [Labour and Brexit] represent."
He said: "If there is a point at which we have to put party loyalty on one side and national interest and our own convictions on the other, then the national interest is going to win."
Lord Heseltine is an ardent critic of the UK's decision to leave the EU, putting him at odds with party colleagues.
The Bow Group, a Conservative think tank, recently demanded he be expelled from the Party's Lords group over a claim he made that a Labour government would be preferable to the "long-term disaster" of Brexit.
The row erupted after comments Lord Heseltine made on a podcast more than a month ago were reported in newspapers this week.
- ITV News political correspondent Paul Brand on Lord Heseltine's comments:
Lord Heseltine told the Limehouse Podcast that a Labour government was preferable to Brexit because any harm it caused could be undone by subsequent governments.
"We've survived Labour governments before. Their damage tends to be short-term and capable of rectification," he said.
"Brexit is not short-term and is not easily capable of rectification.
"There will be those who question whether the short-term pain justifies the avoidance of the long-term disaster."
Among Lord Heseltine's critics is Brexit-supporter Lord Tebbit, the Bow Group's president, who labeled him a "backstabber".
Ben Harris-Quinney, the Bow Group chairman, said that while Conservatives should be allowed to disagree with the party, there was no room for "sabotage".
"Heseltine has made clear it is his aim to prevent Brexit at all costs, including the sabotage of his own Party and nation," he said.
"The Conservative Party must therefore withdraw the whip and end the inevitable continuation of his sniping from inside the tent."
In his interview with ITV News, Lord Heseltine dismissed the comments.