Jackson came from a family of West Riding lawyers: his grandfather had been ‘an attorney in great practice’, and his father, an MP in 1589, succeeded Cuthbert Pepper† as king’s attorney of the Council in the North, and acquired the manors of Hickleton and Womersley, near Pontefract. Jackson inherited this estate of around 2,000 acres on his father’s death in October 1623.
Jackson, one of the few gentry to sign Sir John Savile’s return as knight of the shire at the 1624 general election, stood against Sir Richard Beaumont*, a follower of Savile’s rival, Sir Thomas Wentworth*, at an election at Pontefract on 11 March. Jackson received over 40 voices, including that of the mayor, who duly sealed an indenture with the borough seal, but Beaumont then asked for a poll, only to break it off when it became clear he would lose; his supporters then drafted another indenture. Both returns were forwarded to Westminster, where Savile raised the issue in the Commons on 22 Mar., moving that Jackson be returned on the strength of his majority. Wentworth countered by alleging that Jackson’s supporters included ‘a popish faction’, and that many had been created burgesses for the occasion of the election.
Under the circumstances, it is hardly surprising that Jackson kept a low profile in the Commons. On 15 Apr. he was named to two committees, one for a naturalization bill, the other for the bill for London’s artisan cloth-workers. As a Yorkshire burgess, he also attended meetings of the committees for the Durham enfranchisement bill, and the bill to restrict assignment of private debts to the Crown.
Before the 1625 election Jackson was reconciled with Wentworth, perhaps by his uncle Sir Henry Savile*. He pledged to support Wentworth’s bid for the county seats, and in return Wentworth asked the mayor of Pontefract that ‘Sir John Jackson may be my partner; ... and, in case I should serve in the other place [the county seat], that you then would join Sir Richard Beaumont with Sir John Jackson’. All went according to plan; but, presumably for fear of the plague, Jackson did not take his seat until the day of its dissolution.
In November 1625 Wentworth was pricked as sheriff of Yorkshire to exclude him from the forthcoming Parliament. Jackson promised to ‘endeavour a satisfaction’ for any friend of Wentworth’s at Pontefract in 1626, and the latter accordingly nominated Sir Francis Foljambe, 1st bt.; the pair were returned together. Like many Members, Jackson was little involved in the main business of the session, Buckingham’s impeachment: on 5 Apr. he was one of those who delivered a Remonstrance to the king justifying the decision to charge Buckingham on the grounds of common fame rather than specific evidence; and on 20 May, when the House sought to exonerate (Sir) John Eliot* from allegations of treason arising from his presentation of impeachment charges against the duke - which had led to his arrest - Jackson insisted that he should not be required to withdraw from the chamber unless specific charges were brought against him.
Jackson was more outspoken on the question of religion. At the committee for religion on 6 Mar. he produced a copy of the lord mayor of York’s instructions for the reprieve of condemned Catholic priests, and was ordered, together with secretary of state (Sir) John Coke*, to inquire into its authenticity, which the king eventually admitted. He also attacked Arminian clerics; no theological tenets, he declared, were ‘maintained with more subtle and acute wits’, and while he dismissed Richard Montagu’s works as ‘theoretical and speculative’, he warned that ‘weakness itself, neglected, proves often dangerous’. The bill for ‘continuing of peace and unity in church and commonwealth’, to which committee he was named (14 June), was presumably intended to deal with this problem.
Jackson probably went abroad after the dissolution, but on his return he played a prominent part in resisting the Forced Loan. In January 1627 Viscount Aire, a Scottish peer married to a Yorkshire widow, reported that Jackson had threatened to evict any of his tenants who paid the Loan, adding: ‘by God’s wounds, I could (or would) hang them with my own hands’. Summoned before the Privy Council, he denied the words, but was kept under house arrest in his lodgings in St. Martin’s Lane while attorney-general (Sir) Robert Heath* and Secretary Sir Edward Conway I* searched for a second witness, for ‘it would be very advantageous for the king’s service to have a public hearing of some cause of this nature’.
Wentworth hoped that the former Members would be re-elected at Pontefract in 1628, but Jackson warned that Foljambe would be opposed by Sir John Savile*, recently created steward of the honour. To rid himself of this unwelcome prospect he threatened to stand down, ‘not so much out of fear of the grandees’ opposition as in favour of my own purse; which, a great payment being at this instant upon me, requires some more ease than the ordinary expenses attending parliamentary service will afford me’. Wentworth took the hint, nominating Sir John Ramsden* as Jackson’s partner instead of Foljambe.
After the end of the session, Jackson and Ramsden visited Pontefract, ostensibly to seek instructions from the electorate, but actually to triumph over Savile by hunting within his jurisdiction as gamekeeper of the honour. Savile’s son Sir Thomas ‘struck at Sir John with his drawn sword ... and drove him into a plash of water, ... saying that a pot of ale were fitter for him than a sword’. Wentworth’s elevation to the Lords in July 1628 meant that his friends in the Commons kept a lower profile in the 1629 session, when Jackson’s only committee nomination was to consider a petition against Savile’s management of the recusancy composition scheme in the north (16 February). After the dissolution, he commenced a Star Chamber suit against Sir Thomas Savile for riot, and on 7 June 1632 he was awarded £150 damages.
Jackson enjoyed a reputation for scholarship and literature; some of his Latin verse was published in a eulogy for Sir Rowland Cotton*. He drafted his will on 12 Apr. 1637, shortly before travelling to London for a course of physic, appointing his brothers-in-law Sir William Waller† and (Sir) Richard Hutton*, among others, as trustees for his infant son. He provided detailed instructions for the payment of debts, the raising of portions and the maintenance of his four children. His steward believed that ‘your cure, though difficult, is not pronounced impossible’; but he died on 2 July and was buried near his father in St. Dunstan-in-the West. He was the last of the family to sit in Parliament.