Although WS's public affairs arm is a member of the APPC, the £15,000 payment to Blunkett to speak on 15 March (then just an MP) came from its corporate practice – so WS was not technically in breach of the code.
APPC chair Gill Morris said it had decided to 'review the grey area' over member consultancies that are part of big PR groups.
Blunkett was introduced to Tariq and Lucy Siddiqi of DNA Bioscience, the firm at the centre of his downfall, at the dinner. He declared the WS payment last week prior to resigning.
WS UK & Ireland CEO Colin Byrne said: 'There is nothing wrong with MPs being paid for after-dinner speeches if they abide by parliamentary rules.'