Fergusson was ‘an able man and of a respectable character’,
Fergusson continued to vote with government after 1790. Dundas had thought him a proper person for a seat at the Treasury or at the Admiralty and had commended him to Pitt accordingly. On 29 Jan. 1791 Pitt wrote to the King, recommending that the position of surveyor of crown lands be given to Fergusson, ‘who has been a steady supporter and is capable of being a very useful man of business’. The King acquiesced, but it seems likely that the offer was refused. Had he accepted an office like this one compatible with Parliament, his re-election for Ayrshire was thought secure, but if he accepted one that vacated his seat, there would have been an unwelcome vacuum in Ayrshire.
Fergusson did not seek re-election in 1796. In the following year he declined an appointment to India suggested by the King on account of age,
He died 23 or 25 Sept. 1813. In 1796 he failed to establish his claim, through his mother, to the earldom of Glencairn.
