The Government might have had him for a supporter; it unwisely decided to treat him as an enemy, and for ten years he was an unsparing critic, his popularity increasing with every fresh pamphlet he issued--and at every fresh imprisonment.
Lilburne urged a radical reform of Parliament and a general manhood suffrage in 1647, and the "Case for the Army," published by the Levellers in the same year, on the proposal of the Presbyterian majority in Parliament that the army should be disbanded, demanded the abolition of monopolies, freedom of trade and religion, restoration of enclosed common lands, and abolition of sinecures.
Both Cromwell and Ireton were strongly opposed to manhood suffrage, and Cromwell--to whom the immediate danger was a royalist reaction--had no patience for men who would embark on democratic experiments at such a season.
Lilburne and the Levellers were equally distrustful of Cromwell's new Council of State.

"We were ruled before by King, Lords, and Commons, now by a General, Court-martial, and Commons; and, we pray you, what is the difference ?" So they put the question in 1648.
To Cromwell the one safety for the Commonwealth was in the loyalty of the army to the Government.

To Lilburne the one guarantee for good government was in the supremacy of a Parliament elected by manhood suffrage.

He saw plainly that unless steps were taken to establish democratic institutions there was no future for the Commonwealth; and he took no part in the trial of Charles I., saying openly that he doubted the wisdom of abolishing monarchy before a new constitution had been drawn up.
But Lilburne overestimated the strength of the Leveller movement in the army, and the corporals who revolted were shot by sentence of courts-martial.[59] In vain the democratic troopers argued, "the old king's person and the old lords are but removed, and a new king and new lords with the commons are in one House, and so we are under a more absolute arbitrary monarchy than before." The Government answered by clapping Lilburne in the Tower, where, in spite of a petition signed by 80,000 for his release, he remained for three months without being brought to trial.

Released on bail, Lilburne, who from prison had issued an "Agreement of the Free People," calling for annual parliaments elected by manhood suffrage and the free election of unendowed church ministers in every parish, now published an "Impeachment for High Treason against Oliver Cromwell and his son-in-law, James Ireton," and declared that monarchy was preferable to a military despotism.