Rishi Sunak has warned the Union is "under real risk" as a result of Nicola Sturgeon's plan to hold a second referendum on independence.
The former chancellor, who is battling Liz Truss to become the next leader of the Conservatives, made the comments in a Q&A session with party members last night.
Sunak's leadership campaign has faltered in recent days with his rival now the clear favourite to enter Downing Street.
The Tory MP's team believe they can win over Scottish party members by taking a "firm" stance against an IndyRef2.
Sunak last night branded nationalism as a "seductive and romantic idea".
Asked how he intended to keep Scotland in the Union, Sunak said: "We're under real risk.
"The best things we can do are be firm with Nicola Sturgeon about another referendum. We need to make sure that in government in Whitehall that we don't just devolve and forget, which for many years has been the institutional imperative.
"We as UK Government ministers have to be more active in Scotland, we have to be more active about delivering benefits of the Union on the ground to the people in Scotland and working constructively there to do that.
"And crucially, when you're countering nationalism, we can't just talk in arguments to do with our head.
"It's easy to talk about borrowing and debt and trade and pensions and currency. But ultimately, nationalism is a seductive and romantic idea.
“So we have got to make arguments about the union that speak to people's hearts and speak to their emotions. Because if we focus just on the practicalities, we will not be successful. And I think we can do that.”
The SNP has previously dismissed Sunak's criticisms of independence as "warped".
Speaking earlier this week, SNP MP Kirsten Oswald said: "Rishi Sunak’s warped logic appears to be that the people of Scotland cannot be given a say over their constitutional future because the UK is in such a mess.
"It is precisely because the UK is lagging behind neighbouring countries on a range of wealth and equality indicators – as demonstrated in the recent Scottish Government paper - that independence for Scotland is essential.
"The longer Scotland remains tied to a failing Westminster system, the poorer we will become as a result."
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