The government is setting up a new cabinet committee to focus on the union, sources have told the BBC.
The Cabinet Union Strategy Committee will be chaired by Boris Johnson and "set the government's strategic agenda" for keeping the UK together.
Michael Gove will also play a part, along with the secretaries for Scotland, Wales and Northern Ireland and chief Brexit negotiator Lord Frost.
The news comes after the PM's chief union adviser quit his job.
Oliver Lewis - an ally of the prime minister's former chief adviser, Dominic Cummings - only took up the post three weeks ago, but said his position was made "untenable" by others within Downing Street.
Downing Street declined to comment on staffing matters.
But a senior source told the BBC the union unit that had been run by Mr Lewis would no longer play a key role.
A No 10 spokeswoman confirmed the new unit was being formed and would "build on top of the existing structures" in Downing Street.
She said it would meet regularly and other people outside of the government's Cabinet would attend when needed.
She also said there was already a Union Policy Implementation Committee, led by Mr Gove, which would ensure new policy would be put in place.
The future of the union between England, Scotland, Wales and Northern Ireland is one of the biggest issues facing Mr Johnson.
Elections in Scotland come May could see an SNP government pressing for a new independence referendum.
Post-Brexit issues over trade in Northern Ireland are causing tensions, with unionists saying their position within the UK has been weakened.
And while support for independence in Wales is small, reports suggest the conversation is growing louder.
But the prime minister has said the priority should be "fighting this pandemic and coming back more strongly together", rather than arguing about the constitution.