All select committees have the power to take oral evidence on oath (administered, under Standing Order No. 132, by the Chairman or the Clerk of the Committee). It is not usual for such Committees, other than Committees on private or hybrid Bills, to take evidence on oath although this is done on occasion. The Ministerial Code and the Civil Service Code set the requirements for Ministers and civil servants who give evidence to Select Committees.
I have made no specific assessment of the merits of Committees taking evidence on oath more widely. It is a matter on which each Committee is best placed to take a view in the circumstances of the individual case.