It was three times unlucky for disgraced former Liberal MP Andrew Cornwell and his wife, Samantha Brookes, as they were accused of "covering previous lies with more lies" at a corruption inquiry.

In an extraordinary day at the Independent Commission Against Corruption on Thursday, the once high-flying couple were accused of colluding "to try and fool ICAC" during three separate stints each in the witness box.

The Rex Newell painting in question.

At the centre of their alleged lies was an unprepossessing painting of a boat and a boat shed by Hunter Valley artist Rex Newell.

The pair are accused of participating in a "sham" sale of the painting to disguise an illegal $10,120 payment from local developer Hilton Grugeon.