Haldane entered the sea service of the East India Company.
His parliamentary career is obscure; no speech of his is recorded. His main concern was to secure re-election in 1761 through his great wealth and the interest of his cousin Sir Henry Erskine with Bute. By the purchase of Airthrey, Gleneagles, and property in Dunbartonshire, he increased his interest in three counties; practised extensive bribery in Stirling Burghs; and also cultivated Perth Burghs.
At the general election he stood for Bridport, was defeated, and appealed through Lord Fitzmaurice to Bute, to whom he offered to give up all his Scottish pretensions in return for support in his petition.
He intended to stand again for Bridport at the general election of and also for Stirling Burghs with the support of his friend Sir Lawrence Dundas,
