London, Sept. 12 -- Scotland's highest civil court on Wednesday declared the UK parliament's prorogation by the Boris Johnson government as unlawful, ruling that the move was motivated by the "improper purpose of stymying parliament".

The prorogation until October 14, precipitated by the Brexit issue, took effect in the early hours of Tuesday following criticism by House of Commons speaker John Bercow, among others.

The Supreme Court in London is due to hear another challenge to the prorogation next Tuesday.

Labour and other opposition parties that saw the prorogation as the UK government's bid to avoid scrutiny of its approach to Brexit, hailed the ruling as "historic" and demanded that parliament be recalled immediately. Downing Street...