Borlase’s great-grandfather, of Cornish origin, inherited a Buckinghamshire estate in 1545, and sat for the county in 1586. Borlase endeavoured to remain neutral in the Civil War, but was induced, probably by his father-in-law, to go to Oxford in January 1644, though he denied ever taking his seat in Parliament there. He submitted to Parliament in October 1645, presenting a particular showing an income of £1,590 p.a., and paid a fine of £6,800 in the following year. He was imprisoned at Oxford as a royalist suspect after Penruddock’s rising, and he was under house arrest in April 1658, but he does not seem to have been an active conspirator.3VCH Bucks. iii. 80, 87; Keeler, Long Parl. 111; SP 23/69/822, 831; Cal. Comm. Comp. 919-20; Verney Mems. ii. 11, 124.
Borlase was elected for Wycombe in 1661, and marked as a friend by Lord Wharton, to be managed by Edmund Petty. An inactive Member of the Cavalier Parliament, he was appointed to only nine committees, most of them in the first session and none of political importance. In 1663 he helped to consider a bill for the benefit of the children of his Buckinghamshire neighbour, Bulstrode Whitelocke, but he served on no more committees after 1664, perhaps because of ill-health; for when he was absent from a call of the House in 1668, he escaped a £40 fine on the plea of sickness. He died on 8 Aug. 1672 and was buried at Little Marlow.4CJ, ix. 49, 52; The Gen. n.s. ii. 288.