Why did Macaulay favor parliamentary reform? Is he considered liberal or conservative?

Macaulay was a Whig Member of Parliament. The Whigs later became the Liberal Party, one of the two main political parties in 19th and early 20th century Britain. On the whole, the Whigs were strongly in favor of parliamentary reform; indeed, the 1832 Reform Act stands as one of their greatest achievements.
Ironically, Macaulay was a direct beneficiary of the old corrupt system he wished to see abolished. He represented what was known as a pocket, or rotten borough. This was a name given to a parliamentary seat controlled by a great landowner or family, usually of noble blood. Owners of rotten boroughs, such as Macaulay's patron Lord Lansdowne, regarded these seats as their own private property, theirs to do with as they pleased. Only a handful of people had the right to vote, and even then, there was no secret ballot, so everyone could see how everyone else voted. It was a brave man indeed who would openly defy the will of the local landowner on election day.
Macaulay's support for the Whig government's program of parliamentary reform was conservative rather than radical. The proposed measures, as well as abolishing the notorious rotten boroughs, would greatly expand the electorate, enfranchising a large section of the middle-classes for the very first time. Macaulay, like many Whigs, saw this as a necessary measure to stave off the threat of radical reform, or even outright revolution. He saw the expansion of the franchise as a way of giving more people in society a greater stake in government, making it possible to accommodate their political demands through the democratic process without the need for radical upheaval. The various reform measures, taken as a whole, would bind the nation more closely together, narrowing the dangerous divisions that had developed between Britain's social classes.
https://www.historyofparliamentonline.org/volume/1820-1832/member/macaulay-thomas-1800-1859