Mr Brown will state in a key note speech on Monday that "cosmetic gestures" by Tory Prime Minister Boris Johnson will fail to keep the country together.
The ex-PM will attack what he will describe as "PR gestures" such as suggestions of moving the House of Lords to York, as he insists that only "substantive" moves will keep the union together.
Mr Brown will say that more than cosmetic changes that look good presentationally are needed.
And he will state that the UK will have to change fundamentally so Scotland "does not abandon union" and regions can feel respected in it.
"We must reboot and renew Britain or we risk losing it."
Mr Brown will call for a UK-wide constitutional convention and region-by-region citizens assemblies to gauge public opinion so as to "respond adequately to local needs".
He will say this would act as "forerunner of a new second chamber to replace the House of Lords".
With ministers saying that the Government is considering moving the House of Lords out of London, Mr Brown will say that more needs to be done.
He will say: "An outdated institution 200 miles or so north of its current location is still an outdated institution.
"I will argue for a Council of the North and Council of the Midlands that bring together local authorities, Mayor and MPs and in the form of a Northern Exchequer board take powers from the Treasury over the allocation of regional resources - so that on vital issues, outlying regions and communities will no longer be governed simply by dictates from London second guessing what they want.
"The demand for more power to the north is far greater than can be met by gimmicks or gestures given that the UK is a unitary state but a multinational country; that it is asymmetric with 83% of the votes at elections in England and that political, financial and administrative power has been over-concentrated in one city in the south."