The Queensland MP caught in a sexting scandal has stepped aside as the chair of the parliamentary ethics committee, saying he ‘‘can't and won't’’ defend his behaviour.

The Liberal National Party Member for Redlands Peter Dowling apologised to his wife, children, family and friends for ‘‘the shame and embarrassment I have caused you’’ and pleaded for their privacy.

News Limited reported Mr Dowling, who has been married for 27 years and has two children, had sent a series of explicit text messages and images - including a picture of his penis in a glass of red wine - to his mistress during their two and a half year affair.

In a four-page letter to Queensland Speaker Fiona Simpson, the woman alleged the pair used his parliamentary annexe bedsit and electorate office for sex.