In 1794 he published a pamphlet, Peace and Reform, against War and Corruption, in answer to Arthur Young's The Example of France a Warning to Great Britain.
In 1788, Peter and Daniel Stuart undertook the printing of the Morning Post, a moderate Whig newspaper, which was then owned by Richard Tattersall, and was at a low ebb.
By buying in The Gazetteer and The Telegraph, good management and hiring talented writers, he made the Post a rival to the Morning Chronicle, then the top London daily.
Mackintosh, who wrote regularly for it in its earlier days, introduced Samuel Taylor Coleridge to Stuart in 1797.
On Coleridge's return it was arranged that he should give his whole time to the Morning Post and receive Stuart's largest salary.
An article which Stuart wrote, with Coleridge's assistance, in 1811 on the conduct of the princes in the regency question provoked a speech from the Duke of Sussex in the House of Lords.
In 1817 Stuart obtained a verdict against Daniel Lovell, editor of The Statesman, who had accused him of dishonestly taking money belonging to the Society of the Friends of the People.
Coleridge wrote to Stuart in 1816, praising his journalism for the Courier: It is far, very far, from hyperbole to affirm, that you did more against the French scheme of Continental domination, than the Duke of Wellington has done; or rather Wellington could neither have been supplied by the Ministers, nor the Ministers supported by the Nation, but for the tone first given, and then constantly kept up, by the plain, unministerial, anti-opposition, anti-jacobin, anti-gallican, anti-Napoleonic spirit of your writings, aided by the colloquial good style, and evident good sense, in which as acting on an immense mass of knowledge of existing men and existing circumstances, you are superior to any man I ever met with in my life time.