43. Are there limits on the amount that third parties can spend on election campaign activities?

Source: 

Section 4 (2), Regulation of Election Expenditure Act No. 3 of 2023

4 (2) Where a candidate incurs expenditure in excess of the authorized amount referred to in subsection (3) of section 3 in respect of such election, such candidate commits an offence of an illegal practice within the meaning of the law specified in section 2 under which such election was conducted and, shall be liable to the penalties imposed under such law in respect of the offence of an illegal practice, unless such candidate proves that such expenditure was incurred without any sanction or connivance of such candidate.

https://www.parliament.lk/uploads/acts/gbills/english/6287.pdf 

This is not directly mentioned in the law. However, the offence of spending over the authorised amount implies that the limit applies to all the expenditure by the party/ candidate and on their behalf.